Metals. Part A Unit-based exercise. Topic 3. Unit 10 Occurrence and extraction of metals. Fill in the blanks. True or false

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1 Topic 3 Metals Part Unit-based exercise Unit 10 Occurrence and extraction of metals Fill in the blanks 1 Light bulb filaments are made of tungsten. 2 The two most abundant metals in the Earth s crust are aluminium and iron. 5 The common ore of aluminium is bauxite. It consists of aluminium oxide mainly. luminium is extracted from its ore by electrolysis. True or false ecide whether each of the following statements is true or false. Part Unit 10 3 Lead can be extracted from lead(ii) sulphide. a) First change the sulphide into oxide by heating. lead(ii) sulphide + oxygen lead(ii) oxide + sulphur dioxide b) Then remove oxygen from the oxide using carbon. lead(ii) oxide + carbon lead + carbon dioxide 4 a) uring the extraction of iron in a blast furnace, a mixture of iron ore, coke and limestone is added at the top of the furnace. b) Hot air is blown into the bottom of the furnace. chain of chemical reactions occurs. c) arbon dioxide reduces iron(iii) oxide in the ore, producing iron. iron(iii) oxide + carbon monoxide iron + carbon dioxide 6 Electric wire is made of bronze but not F of pure copper. 7 Historically, gold was mainly used for T ornaments. 8 admium is used in making rechargeable T cells. 9 Iron is the most abundant metal in the F Earth s crust. 10 innabar is a common ore of mercury. T 11 Galena consists mainly of lead(ii) oxide. F 12 Zinc blende consists mainly of zinc T sulphide. 13 Iron can be extracted by heating its ore F in air. 14 t the temperature of unsen flame, F carbon can remove oxygen from zinc oxide. 15 Magnesium is extracted from its ore by T electrolysis. 1

2 Part Unit opper was the first metal extracted T from its ore. 17 The Iron ge came after the ronze ge. T 18 ronze is an alloy of copper and tin. T 19 luminium was used earlier than iron. F 20 rass is softer than pure copper. F Multiple choice questions irections: Questions 21 and 22 refer to the following information. Iron is about twice as strong as aluminium. Some other properties of aluminium and iron are shown in the table. Electrical conductivity ensity (g cm 3 ) orrosion resistance luminium very good 2.7 good Iron good 7.9 poor 23 luminium has a low density and good electrical conductivity. Which of the following uses of aluminium depends on OTH of these properties? For cooking pans For aeroplanes For overhead power cables For racing cars 24 Which of the following objects is LEST likely to contain titanium? Tooth implants Spectacles Watch cases Water taps 25 Which of the following combinations concerning the use of metals is correct? Metal hromium opper Lithium Zinc Use making duralumin making fuse in electric plugs making dry cells making cans for canned food 21 Iron is better than aluminium for making bridges. This is because iron is a better insulator. is more easily painted. is stronger. has a higher density. 22 luminium is better than iron for making cans for fizzy drinks. The main reason is that aluminium conducts electricity better. aluminium is harder. iron cannot be recycled. aluminium is more resistant to corrosion. 26 Which of the following combinations concerning the use of metal is INORRET? Metal Use luminium window frames Magnesium railings Tin coating for other metals Tungsten light bulb filaments 27 Which of the following statements concerning silver is correct? It is an excellent conductor of electricity. It is very strong. It has a low density. It is the third most abundant metal in the Earth s crust. 2

3 28 Gold ornaments are usually made from an alloy of gold and copper instead of pure gold. This is because the alloy can be found free in nature. is more corrosion resistant than pure gold. is more ductile than pure gold. is stronger than pure gold. 29 Which of the following is a common ore of iron? alcite innabar Gypsum Haematite 30 Which of the following is a common ore of lead? arnallite Galena Rock salt Silica 31 The main metallic compound in magnesite is magnesium carbonate. magnesium chloride. magnesium oxide. magnesium sulphate. 34 The diagram shows a method for changing a metal oxide into a metal. Which of the following oxides can be changed into a metal by this method? alcium oxide opper(ii) oxide Magnesium oxide Potassium oxide irections: Questions 35 and 36 refer to the following electrolytic cell used to obtain aluminium from aluminium oxide. Part Unit Mercury is extracted from its ore by heating in air. heating with carbon. electrolysis. mechanical separation. 33 onsider the following word equation: mercury(ii) sulphide + oxygen heat X + Y Which of the following combinations is correct? X Mercury sulphur Mercury sulphur dioxide Mercury(II) oxide sulphur Mercury(II) oxide sulphur dioxide Y 35 From which substance are the electrodes made of? Graphite Iron Sulphur Zinc 36 The positive electrodes are replaced frequently because they react with aluminium. aluminium oxide. cryolite. oxygen. 3

4 Part Unit Which of the following combinations is INORRET? Metal Method of extraction luminium electrolysis of molten ore opper controlled heating in air Iron heating with carbon Silver heating with carbon 38 Which of the following periods came after the ronze ge? lloy ge opper ge Iron ge Stone ge 39 Which of the following metals was NOT discovered in ancient times? Gold Magnesium Mercury Silver 42 Which of the following metals can be found as free elements in the Earth s crust? (1) Gold (2) Silver (3) Zinc (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 43 Which of the following statements concerning aluminium is / are correct? (1) It is the most abundant element in the Earth s crust. (2) It is obtained from its oxide by electrolysis. (3) It is used to make stainless steel. (1) only (2) only (1) and (3) only (2) and (3) only 40 luminium can be obtained by extracting it from aluminium ore, and by recycling used aluminium objects. Which of the following is a ISVNTGE of extracting aluminium from its ore? luminium ore contains very small amounts of aluminium. luminium ore is a limited resource. The aluminium obtained corrodes easily. The aluminium obtained has a high density. 41 luminium is used to make cooking foil because (1) it is very malleable. (2) it can resist corrosion. (3) it is a good conductor of heat. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 44 Which of the following statements concerning copper are correct? (1) It was the first metal extracted from its ores. (2) It is a very good conductor of electricity. (3) It is used to make water pipes for carrying hot water. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 45 Which of the following statements concerning iron are correct? (1) It has a high tensile strength. (2) It is the most abundant metal in the Earth s crust. (3) It is extensively recycled. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 4

5 46 Which of the following statements concerning lead is / are correct? (1) It is found in solder. (2) It exists as lead(ii) oxide in its ore of galena. (3) It is extracted by heating its ore in air. (1) only (2) only (1) and (3) only (2) and (3) only 47 Which of the following statements concerning titanium are correct? (1) It has a high tensile strength. (2) It is used to make replacement hip joints. (3) Its density is lower than that of aluminium. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 48 luminium is extracted from its oxide by electrolysis. Which of the following statements concerning the extraction process are correct? (1) The process is carried out in a large steel tank. (2) The electrodes are made of graphite. (3) Oxygen gas bubbles off from the negative electrodes. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 49 In which of the following ores do the metals exist mainly as sulphides? (1) auxite (2) innabar (3) opper pyrite (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 50 Which of the following metals can be extracted by heating the ores alone? (1) opper (2) Mercury (3) Zinc (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 51 Which of the following metals are extracted by reduction with carbon? (1) Iron (2) Lead (3) Magnesium (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 52 Which of the following statements concerning the extraction of iron are correct? (1) It is carried out in a blast furnace. (2) Limestone is produced in the process. (3) Iron(III) oxide reacts with carbon monoxide to give iron. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 53 In which of the following processes would a metal be produced? (1) Heating mercury(ii) sulphide (2) Heating iron(iii) oxide (3) Heating lead(ii) oxide with carbon (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) Part Unit 10 5

6 54 The price of a metal depends mainly on (1) its abundance in the Earth s crust. (2) the extraction method used. (3) the cost of mining its ore. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 55 Which of the following are possible ways to conserve metals? (1) Recycle metal cans. (2) Reuse metal articles. (3) Replace metals with other materials. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) Part Unit 10 irections : Each question (Questions 56 60) consists of two separate statements. ecide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from to according to the following table : oth statements are true and the 2nd statement is a correct explanation of the 1st statement. oth statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. The 1st statement is false but the 2nd statement is true. oth statements are false. 1st statement 2nd statement 56 Titanium is used to make space shuttles. Titanium is light and strong. 57 Electric wires are made of brass but not of rass is more corrosion resistant than copper. copper. 58 Pure copper, rather than brass, is commonly opper is softer than brass. used for making ornaments. 59 luminium was used earlier than iron in the luminium is more abundant than iron in the history of mankind. Earth s crust carat gold is an alloy. 24-carat gold is made of gold and copper. 6

7 Unit 11 Reactivity of metals Fill in the blanks 1 When potassium is heated in air, it burns with a flame of lilac colour. smoke of white colour forms. potassium + oxygen potassium oxide 2 When calcium is heated in air, it burns with a flame of brick-red colour. powder of white colour forms. calcium + oxygen calcium oxide 3 When magnesium is heated in air, it burns with a very bright light. powder of white colour forms. magnesium + oxygen magnesium oxide 8 Iron reacts with dilute sulphuric acid and dilute hydrochloric acid to produce salts and hydrogen gas. iron + dilute sulphuric acid iron(ii) sulphate + hydrogen iron + dilute hydrochloric acid iron(ii) chloride + hydrogen 9 a) Metals at the top of the reactivity series are extracted by electrolysis. b) Metals in the middle are extracted by reduction of their oxides with carbon. c) Metals near to the bottom are extracted from their ores by heating in air. 10 When zinc reacts with copper(ii) sulphate solution, zinc sulphate solution and copper deposits form. Part Unit 11 4 When zinc is heated in air, a powder forms. The colour of the powder is yellow when hot but white when cold. zinc + oxygen zinc oxide 5 When iron is heated in air, it burns with sparks. solid of black colour forms. iron + oxygen iron(ii, III) oxide 6 When sodium reacts with cold water, the metal melts to form a bead. Sodium burns with a flame of golden yellow colour. sodium + water sodium hydroxide + hydrogen 7 Magnesium reacts readily with steam. magnesium + steam magnesium oxide + hydrogen True or false ecide whether each of the following statements is true or false. 11 Magnesium burns with a very bright light. T 12 Silver burns in air to give silver oxide. F 13 Iron burns with a bluish green flame. F 14 luminium gives a white powder when T burnt in air. 15 Lead gives a black powder when heated F in air. 16 Magnesium is kept in paraffin oil in the F laboratory. 17 Potassium burns with a lilac flame when T reacting with water. 18 alcium floats on water. F 7

8 19 Sodium reacts with water to give an T alkaline solution. 20 Magnesium reacts readily with cold water F to give hydrogen. 21 Zinc reacts with steam to give zinc oxide T and hydrogen. 22 When iron reacts with dilute sulphuric F acid, iron(iii) sulphate is formed. 28 In an experiment, sodium is put into a trough of water. What are the products formed? Sodium hydroxide and hydrogen Sodium hydroxide and oxygen Sodium oxide and hydrogen Sodium oxide and oxygen 29 student used the following set-up to study the reaction of metal X with cold water. gas was produced in the process. 23 Zinc atoms lose electrons more easily T than copper atoms. Part Unit Metals at the top of the reactivity series F are extracted by reduction of their oxides with carbon. 25 Iron(III) oxide can be reduced to iron by T heating with aluminium powder. Multiple choice questions Metal X could be aluminium. calcium. lead. lithium. 26 Magnesium is heated in air. Which of the following combinations is correct? Observation bright light is observed bright light is observed golden yellow flame is observed golden yellow flame is observed Product yellow powder white powder white powder yellow powder 27 When a flame test is carried out on copper(ii) sulphate, what is the colour of the flame observed? luish green rick-red Golden yellow Lilac 30 Results of some experiments on a metal X are listed below: X burns when heated in air. X reacts with water to give a hydroxide. X cannot be extracted from its oxide by carbon reduction. X could be iron. magnesium. potassium. zinc. 31 arium (a) is a Group II element of the periodic table. Its relative atomic mass is greater than that of calcium. Which of the following statements concerning barium is INORRET? It reacts vigorously with water. It reacts with water to give barium oxide. It sinks in water. Its melting point is lower than that of calcium. 8

9 32 In an experiment, steam is passed over aluminium. What are the products formed? luminium hydroxide and hydrogen luminium hydroxide and oxygen luminium oxide and hydrogen luminium oxide and oxygen 33 onsider the following experiment. 37 ilute hydrochloric acid is added to a test tube containing several small pieces of iron. Which of the following observations is correct? There is no observable change. thick white precipitate forms. colourless gas is produced and the test tube warms up. colourless gas is produced and the test tube cools off. 38 In which of the following sets are the metals arranged in descending order of reactivity? uring the experiment, a gas is produced. X could be copper. gold. lead. magnesium. a, Na, Zn, Pb, l, u Zn, u, a, l, Na, Pb Na, l, Zn, a, Pb, u Na, a, l, Zn, Pb, u 39 The following table shows results of the reactions of three metals (X, Y and Z). Part Unit Which of the following metals is the most suitable for making a container to hold hot water? opper Lead Magnesium Silver 35 Which of the following sets of substances are formed when zinc reacts with dilute sulphuric acid? Zinc sulphate and hydrogen Zinc sulphate and sulphur dioxide Zinc sulphide and hydrogen Zinc sulphide and sulphur dioxide 36 Which of the following pairs of chemicals do NOT react when mixed? Magnesium and dilute sulphuric acid alcium and water Iron and steam Silver and dilute hydrochloric acid Experiment Heating in air Reaction with water Metal X Y Z a powder formed bubbles given off no observable change no observable change a powder formed no observable change The reactivity series for the metals in order of increasing reactivity is X < Y < Z. X < Z < Y. Y < X < Z. Y < Z < X. 40 Metal X is in between iron and lead in the reactivity series. Which of the following statements concerning X is probably correct? It can be found free in the Earth s crust. It shows no observable change when heated in air. It can be obtained by reduction of its oxide with carbon. It reacts with cold water to give hydrogen. 9

10 Part Unit The equation below represents the reaction of aluminium with dilute hydrochloric acid. wl + xhl yll 3 + zh 2 Which of the following combinations is correct? w x y z Magnesium reacts with ammonia according to the following equation: xmg + ynh 3 Mg 3 N 2 + zh 2 Which of the following combinations is correct? x y z The action of dilute sulphuric acid on iron(iii) hydroxide can be represented by the following equation: xfe(oh) 3 + yh 2 SO 4 What is the value of z? Fe 2 (SO 4 ) 3 + zh 2 O 46 In limestone areas, calcium carbonate in the rock reacts with rainwater containing dissolved carbon dioxide as shown by the following equation: ao 3 (x) + O 2 (g) + H 2 O(y) a(ho 3 ) 2 (z) Which of the following combinations is correct? x y z aq l s aq aq s s aq aq s l aq 43 The equation below represents the reaction of chlorine with hot concentrated potassium hydroxide solution: 3l 2 + xkoh ykl + KlO 3 + zh 2 O Which of the following combinations is correct? x y z onsider the following chemical equation: 3Zn + xhno 3 What is the value of y? Zn(NO 3 ) 2 + yno + zh 2 O 47 onsider the following reaction: ZnO(x) + H 2 SO 4 (y) ZnSO 4 (z) + H 2 O(l) Which of the following combinations is correct? x y z s aq aq aq aq s s l l aq l aq 48 The following equation represent the reaction of an oxide of lead with hydrogen: Pb 3 O 4 (x) + 4H 2 (y) 3Pb(s) + 4H 2 O(z) Which of the following combinations is correct? x y z s g l aq l l aq l aq s g aq 10

11 49 Which of the following pairs of substances will react when mixed? 50 Into each of the following four solutions, a piece of copper is added. (I) silver nitrate solution copper (II) iron(ii) nitrate solution copper (III) zinc nitrate solution copper (IV) magnesium nitrate solution copper Which of the following combinations is correct? Tube Observation I no observable change II grey coating on copper III reddish brown coating on copper IV no observable change 51 onsider the results of displacement reactions of three different metals, P, Q and R. Metal Solution of nitrate of P Q R The descending order of reactivity of the metals is R > P > Q. P > Q > R. R > Q > P. Q > R > P. 52, and are three different metals. The table below lists the observations when each of them is put into copper(ii) nitrate solution. Metal Observations a brown solid formed no observable change a brown solid formed and a colourless gas evolved Which of the following sequences correctly represents the ascending order of reactivity of the metals? < < < < < < < < 53 X and Y are two different metals. Which of the following shows that X is more reactive than Y? X forms an ion with a charge of +2 while Y forms an ion with a charge of +1. X can displace Y from an aqueous solution of a salt of Y. When the oxide of X is heated with Y, X is formed. The oxide of X undergoes decomposition upon strong heating but the oxide of Y does not. Part Unit 11 P Q R Key: = reaction = no reaction 54 Which of the following ionic equations best represents the reaction between copper and silver nitrate solution? u(s) + g + (aq) u(s) + 2g + (aq) 2u(s) + g 2+ (aq) u(s) + g 2+ (aq) u + (aq) + g(s) u 2+ (aq) + 2g(s) 2u + (aq) + g(s) u 2+ (aq) + g(s) 11

12 Part Unit X, Y and Z are three different metals. Only Y is found as a free element in the Earth s crust. arbon can remove oxygen from the oxide of X but not from that of Z. The reactivity series of these metals in decreasing reactivity is X > Z > Y. Y > Z > X. Z > X > Y. Y > X > Z. 56 The following table shows some information about four different metals, W, X, Y and Z. Metal Year of discovery Extraction W 1746 carbon reduction X ancient mechanical separation Y ancient carbon reduction Z 1826 electrolysis of molten ore irections: Questions 58 and 59 refer to the results of experiments of three different metals X, Y and Z, and their oxides. Experiment ction of metal on zinc sulphate solution ction of heat on metal oxide Metal X Y Z no observable change a solid with metallic lustre is formed a gas is given off no observable change no observable change no observable change 58 Which of the following arrangements represents the order of increasing reactivity of the three metals? X < Z < Y Y < X < Z Y < Z < X Z < X < Y Which of the metals is the most reactive? W X Y Z 57 hromium lies between zinc and iron in the reactivity series. Which of the following statements is INORRET? When chromium powder is added to copper(ii) sulphate solution, a brown deposit forms. hromium reacts with dilute hydrochloric acid to liberate hydrogen. Magnesium is more reactive than chromium. hromium is usually obtained by electrolysis of its molten ore. 59 Which of the following statements concerning Y is probably correct? (1) Y can be obtained by heating its oxide with zinc powder. (2) Y can be extracted from its ore by electrolysis. (3) Y has been used by humans since ancient times. (1) only (2) only (1) and (3) only (2) and (3) only 60 From which of the following processes can copper be obtained in a school laboratory? dding silver to copper(ii) sulphate solution Mixing copper(ii) oxide with carbon Passing hydrogen over hot copper(ii) oxide Passing electricity through solid copper(ii) sulphide 12

13 61 metal gives a white powder when heated in air. The metal could be (1) aluminium. (2) iron. (3) mercury. (1) only (2) only (1) and (3) only (2) and (3) only 62 Lithium is a Group I element. Which of the following statements concerning lithium are correct? (1) Lithium burns in air to form an oxide. (2) mong the Group I elements, lithium atoms lose electrons most readily. (3) Lithium is used to make rechargeable dry cells. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 63 Metal X forms a black oxide when it is burnt in air. It shows no reaction with dilute sulphuric acid. X could be (1) copper. (2) iron. (3) lead. (1) only (2) only (1) and (3) only (2) and (3) only 64 small piece of calcium is put into a trough of water. Which of the following observations is / are correct? (1) slight explosion occurs. (2) olourless gas bubbles evolve. (3) alcium moves rapidly on the water surface. (1) only (2) only (1) and (3) only (2) and (3) only 65 aesium (s) is an alkali metal. Which of the following statements are correct? (1) It loses electrons more readily than potassium does. (2) It tarnishes rapidly in air. (3) It reacts with water to give an alkaline solution. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 66 Which of the following processes will produce an oxide? (1) dding calcium to water (2) Heating magnesium in air (3) Passing steam over heated aluminium (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 67 When calcium granules are added to water, colourless gas bubbles are formed. The mixture is then filtered to obtain a clear solution. Which of the following is / are correct if carbon dioxide gas is bubbled into the clear solution? (1) Gas bubbles form. (2) white precipitate forms. (3) The clear solution turns from colourless to brick-red. (1) only (2) only (1) and (3) only (2) and (3) only 68 ilute sulphuric acid has NO reaction with (1) gold. (2) magnesium. (3) silver. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) Part Unit 11 13

14 Part Unit In which of the following processes would hydrogen be produced? (1) dding zinc granules to dilute sulphuric acid (2) Passing steam over heated iron powder (3) Electrolysis of acidified water (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 70 Which of the following actions are dangerous and should NOT be attempted in a school laboratory? (1) Heating calcium in steam (2) dding sodium to dilute sulphuric acid (3) isposing a piece of potassium to a rubbish bin (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 71 counterfeit gold coin is made from an alloy of copper and zinc. Which of the following methods can be used to show that the coin is NOT made of pure gold? (1) etermining its tensile strength (2) etermining its density (3) Treating it with dilute sulphuric acid (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 72 X and Y are two different metals. Which of the following show(s) that Y is more reactive than X? (1) X forms an ion with a charge of +2 while Y forms an ion with a charge of +3. (2) The oxide of X can be reduced by heating with carbon but the oxide of Y cannot. (3) X reacts with dilute hydrochloric acid but Y does not. (1) only (2) only (1) and (3) only (2) and (3) only 73 piece of copper was placed into silver nitrate solution. Which of the following observations are correct? (1) grey solid formed. (2) The solution became blue in colour. (3) colourless gas was evolved. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 74 When a piece of iron is dropped into an aqueous solution of X, the iron gradually dissolves. X could be (1) calcium nitrate. (2) copper(ii) sulphate. (3) silver nitrate. (1) only (2) only (1) and (3) only (2) and (3) only 75 X and Y are two different metals. X reacts with the solution of nitrate of Y according to the following equation: X(s) + Y 2+ (aq) X 2+ (aq) + Y(s) Which of the following deductions is / are correct? (1) oth X and Y can react with water. (2) The reactivity of X is higher than that of Y. (3) The oxide of Y undergoes decomposition upon strong heating but the oxide of X does not. (1) only (2) only (1) and (3) only (2) and (3) only 14

15 76 onsider the following reactions of four different metals, Zn, Mg, X and Y. 78 In which of the following experiments would a metal be produced? (1) Heating silver oxide (2) Heating iron pyrite (3) Heating copper(ii) oxide with magnesium (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) The results are: Tube 1 Tube 2 Tube 3 grey coating on X no observable change mud-like deposit on X ased on the experimental results, which of the following deductions are correct? (1) Magnesium is more reactive than X. (2) X is more reactive than Y. (3) Y is more reactive than zinc. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 77 From which of the following processes can lead be obtained in a school laboratory? (1) dding zinc to dilute lead(ii) nitrate solution (2) Heating lead(ii) oxide strongly (3) Mixing lead(ii) oxide with carbon (1) only (2) only (1) and (3) only (2) and (3) only 79 Metal X is discovered recently. Results of some reactions of this metal are listed in the following table. Results of reactions X does not react with water. X reacts with dilute hydrochloric acid to give hydrogen gas. X displaces iron from iron(ii) nitrate solution. Which of the following statements concerning X are probably correct? (1) X reacts with steam. (2) X displaces copper from copper(ii) sulphate solution. (3) X can be obtained from its oxide by heating with iron powder. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 80 In which of the following processes will reaction(s) take place? (1) dding calcium to dilute hydrochloric acid (2) dding zinc to magnesium nitrate solution (3) Mixing copper(ii) oxide with charcoal powder (1) only (2) only (1) and (3) only (2) and (3) only Part Unit 11 15

16 irections : Each question (Questions 81 88) consists of two separate statements. ecide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from to according to the following table : oth statements are true and the 2nd statement is a correct explanation of the 1st statement. oth statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. The 1st statement is false but the 2nd statement is true. oth statements are false. 1st statement 2nd statement Part Unit Sodium appears dull when exposed to air. It reacts with oxygen in the air to form an oxide layer. 82 ll metals react with dilute sulphuric acid to ilute sulphuric acid contains hydrogen. give hydrogen gas. 83 Zinc reacts less vigorously with dilute hydrochloric Zinc is less reactive than iron. acid than iron. 84 When magnesium is added to dilute sulphuric Magnesium atoms donate electrons to acid, hydrogen gas is evolved. hydrogen ions and hydrogen molecules are formed. 85 Potassium is more reactive than sodium. Potassium atoms lose electrons more readily than sodium atoms. 86 Lead can displace iron from iron(ii) nitrate Lead occupies a higher position in the reactivity solution. series than iron. 87 When sodium is added to zinc chloride solution, Sodium is higher than zinc in the reactivity a layer of zinc would form on the surface of series. sodium. 88 Magnesium can be extracted from its oxide by Magnesium is above copper in the reactivity heating with copper powder. series. 16

17 Unit 12 Reacting masses Fill in the blanks 1 One mole is the amount of a substance that contains the same number of particles as there are atoms in 12.0 g of carbon-12 ( 12 6). 2 The mass of one mole of a substance is called its molar mass. The units are gram per mole. 3 The water in hydrated magnesium chloride (Mgl 2 6H 2 O) is called water of crystallization. 9 One mole of nitrogen molecules contains T two moles of nitrogen atoms. 10 One mole of ammonium dichromate F contains four moles of ions. 11 One mole of aluminium atoms can form F 3 x 6.02 x l 3+ ions. 12 Two moles of sulphur dioxide molecules T contain four moles of oxygen atoms. 13 The number of atoms in 1 mole of T O 2 (g) is less than that in 1 mole of O 3 (g). 14 The mass of one mole of a substance T is its molar mass. 4 When hydrated crystals are heated, the water is driven off, leaving behind an anhydrous solid. 5 The empirical formula of a compound gives the simplest whole number ratio of atoms or ions present in the compound. 6 The molecular formula of a compound gives the actual number of atoms in a molecule of the compound. 15 The molar mass of a substance has no F unit as it is a ratio. 16 The empirical formula of a compound F gives the simplest whole number ratio of molecules present in the compound. 17 nhydrous copper(ii) sulphate has the F chemical formula uso 4 5H 2 O. 18 The empirical and molecular formulae F of a compound are always the same. Part Unit 12 True or false ecide whether each of the following statements is true or false. 7 One mole is the amount of a substance F that contains the same number of ions as there are atoms in 12.0 g of carbon The coefficients before the reactant(s) T and product(s) in a chemical equation indicate the mole ratio of the reactant(s) and product(s). 20 The actual yield of a reaction is often T less than the theoretical yield. 8 The vogadro constant equals to T 6.02 x mol 1. 17

18 Part Unit 12 Multiple choice questions 21 The vogadro constant is the same as the number of molecules in 1 g of hydrogen. atoms in 16 g of sulphur. atoms in 24 g of carbon. molecules in 32 g of oxygen. (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, S = 32.1) 22 How many atoms are there in 4.50 moles of magnesium atoms? (vogadro constant = 6.02 x mol 1 ) 2.71 x x x x What is the number of moles of ions in 9.03 x sodium ions? (vogadro constant = 6.02 x mol 1 ) 1.00 mole 1.50 moles 2.00 moles 2.50 moles 26 What is the number of moles of ions in 1 mole of calcium phosphate? 2 moles 3 moles 4 moles 5 moles 27 One mole of magnesium chloride contains two moles of magnesium ions and one mole of chloride ions x magnesium ions and 2 x 6.02 x chloride ions. equal number of magnesium ions and chloride ions. 1 magnesium ion and 2 chloride ions. 28 Which of the following contains the largest number of moles of ions? 2 moles of aluminium sulphate 2 moles of calcium chloride 3 moles of zinc oxide 4 moles of potassium nitrate 29 Which of the following has the greatest number of ions? 5 moles of aluminium fluoride 6 moles of iron(iii) chloride 7 moles of copper(ii) nitrate 8 moles of potassium permanganate 24 How many atoms are present in 6.00 moles of carbon dioxide molecules? (vogadro constant = 6.02 x mol 1 ) 1.08 x x x x How many ions are present in mole of sodium sulphide? (vogadro constant = 6.02 x mol 1 ) 2.11 x x x x How many moles of silane (SiH 4 ) contain y hydrogen atoms? (L represents the vogadro constant.) y L L y y 4L 4y L 18

19 31 Element X forms two oxides XO and X 2 O 3. If 1 mole of XO contains n atoms, 1 mole of X 2 O 3 would contain 2 5 n atoms. 5 2 n atoms. 2n atoms. 5n atoms. 32 Which of the following has the greatest mass? (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0, Na = 23.0) mole of O mole of Na 2 O moles of H 3 OOH 2.00 moles of NH 3 33 How many moles of atoms are there in 4.80 g of sulphur? (Relative atomic mass: S = 32.1) mole mole mole 1.00 mole 34 How many moles of formula units (aso 4 2H 2 O) are there in 60.2 g of calcium sulphate-2- water? (Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, a = 40.1) mole mole mole mole 35 How many molecules are there in 51.0 g of ammonia? (Relative atomic masses: H = 1.0, N = 14.0; vogadro constant = 6.02 x mol 1 ) x 6.02 x x 6.02 x How many ions are there in 202 g of magnesium nitride? (Relative atomic masses: N = 14.0, Mg = 24.3; vogadro constant = 6.02 x mol 1 ) x 6.02 x x 6.02 x If 6.75 g of aluminium contain x atoms, how many atoms are present in 24.0 g of carbon? (Relative atomic masses: = 12.0, l = 27.0) 3x 4x 6x 8x 38 If 1 mole of oxygen (O 2 ) contains x atoms, 2 moles of ozone (O 3 ) will contain 3 2 x atoms. 2x atoms. 3x atoms. 6x atoms. 39 What mass of carbon dioxide has the same number of molecules as 21.9 g of hydrogen chloride? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, l = 35.5) 26.4 g 28.2 g 30.0 g 31.8 g 40 Which of the following contains the same number of atoms as there are in 8.00 g of oxygen? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, Ne = 20.2, Si = 28.1) 1.00 g of hydrogen 18.0 g of carbon 10.1 g of neon 28.1 g of silicon Part Unit 12 19

20 41 Which of the following samples of gases contains the SMLLEST number of molecules? 45 Which of the following statements concerning 2 moles of ammonia is INORRET? Part Unit 12 (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0, S = 32.1) 10 g of NO 2 10 g of SO 2 10 g of O 10 g of H 4 42 Which of the following has the greatest number of ions? (Relative atomic masses: O = 16.0, Na = 23.0, Mg = 24.3, l = 35.5, a = 40.1, Fe = 55.8, r = 79.9) 12 g of calcium chloride 14 g of magnesium oxide 16 g of iron(iii) chloride 18 g of sodium bromide 43 The molecular formula of a gaseous element X is X g of the gas contain 2.50 moles of molecules. What is the relative atomic mass of X? Which of the following statements concerning 32.0 g of oxygen gas is correct? (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0 ; vogadro constant = 6.02 x mol 1 ) (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0, l = 35.5 ; vogadro constant = 6.02 x mol 1 ) It contains 2 moles of nitrogen atoms. It contains 6 x 6.02 x hydrogen atoms. It contains the same number of atoms as 4 moles of hydrogen chloride. It contains the same number of atoms as 44.0 g of carbon dioxide. 46 What is the percentage by mass of potassium in potassium carbonate? (Relative atomic masses: = 12.0, O = 16.0, K = 39.1) 28.1% 42.2% 56.6% 84.4% 47 What is the percentage by mass of water in uso 4 5H 2 O? (Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, u = 63.5) 36.1% 41.8% 52.3% 66.4% 48 The compound X 2 ro 4 contains 65.1% of X by mass. What is the relative atomic mass of X? It contains the same number of molecules as 28.0 g of nitrogen gas. It contains the same number of molecules as 34.0 g of ammonia gas. It contains 6.02 x oxygen atoms. It contains the same number of atoms as 12.0 g of carbon. (Relative atomic masses: O = 16.0, r = 52.0)

21 49 Hydrated sodium carbonate Na 2 O 3 nh 2 O contains 60.4% by mass of water. What is the value of n? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, Na = 23.0) Metal X forms an oxide g of this oxide contain 49.7 g of X. What is the mole ratio of X to oxygen in the oxide? (Relative atomic masses: O = 16.0, X = 207.2) 1 : 2 1 : 3 2 : 3 3 : 4 51 In a compound formed between copper and oxygen, it is found that 25.4 g of copper combine with 3.20 g of oxygen. What is the empirical formula of the compound? (Relative atomic masses: O = 16.0, u = 63.5) u 2 O uo uo 2 u 2 O 3 52 n alcohol contains 60.0% carbon, 13.3% hydrogen and 26.7% oxygen. What is its empirical formula? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0) 2 H 6 O 3 H 8 O 4 H 10 O 5 H 12 O 53 The formula of hydrated zinc sulphate is ZnSO 4 xh 2 O g of the hydrated sulphate are heated to drive away the water g of residue are left. What is the value of x? (Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Zn = 65.4) student heated some Epsom salts (MgSO 4 7H 2 O) in a crucible at 100. The following results are obtained: Mass of crucible = g Mass of crucible + Epsom salts = g Mass of crucible + residue after heating = g What is the chemical formula of the residue? (Relative atomic masses: H = 1.0, O = 16.0, Mg = 24.3, S = 32.1) MgSO 4 MgSO 4 2H 2 O MgSO 4 4H 2 O MgSO 4 5H 2 O 55 compound X contains 82.8% carbon and 17.2% hydrogen. Its relative molecular mass is What is its molecular formula? (Relative atomic masses: H = 1.0, = 12.0) 2 H 5 4 H 10 6 H 15 8 H g of metal X combine with 2.16 g of oxygen to form an oxide in which the charge of the ion of X is +3. What is the relative atomic mass of X? (Relative atomic mass: O = 16.0) Part Unit 12 21

22 Part Unit Fe(OH) O H 2 O...Fe(OH) 3 1 mole of O 2 reacts with Fe(OH) 2 according to the reaction represented by the above equation. How many moles of Fe(OH) 3 can be obtained? Magnesium and titanium(iv) chloride react according to the following chemical equation: Til 4 (g) + 2Mg(l) Ti(s) + 2Mgl 2 (l) What is the mass of magnesium required to react completely with 114 g of titanium(iv) chloride? (Relative atomic masses: Mg = 24.3, l = 35.5, Ti = 47.9) 14.6 g 29.2 g 43.8 g 58.4 g g of calcium carbonate decompose completely on heating. What is the mass of calcium oxide obtained? (Relative atomic masses: = 12.0, O = 16.0, a = 40.1) 3.01 g 3.61 g 4.21 g 4.81 g 60 onsider the following chemical equation: Fe 2 O 3 (s) + 3O(g) 2Fe(s) + 3O 2 (g) 83.7 g of iron are formed. What is the mass of iron(iii) oxide consumed? (Relative atomic masses: O = 16.0, Fe = 55.8) 80 g 120 g 160 g 200 g 61 The removal of silicon dioxide with limestone in a blast furnace can be represented by the following equation: ao 3 (s) + SiO 2 (s) asio 3 (l) + O 2 (g) What is the mass of calcium carbonate needed to remove 1.00 tonne of silicon dioxide? (Relative atomic masses: = 12.0, O = 16.0, Si = 28.1, a = 40.1; 1 tonne = 10 6 g) 0.46 tonne 0.60 tonne 1.67 tonnes 2.18 tonnes 62 onsider the following chemical reaction of an oxide of lead with hydrogen: Pb 3 O 4 (s) + 4H 2 (g) 3Pb(s) + 4H 2 O(l) 178 g of the lead oxide are consumed in the reaction. What is the mass of lead obtained? (Relative atomic masses: O = 16.0, Pb = 207.2) 106 g 117 g 131 g 162 g 63 Thermal decomposition of KlO 3 (s) gives Kl(s) and O 2 (g) as the only products. What is the mass of oxygen produced when 24.5 g of KlO 3 (s) undergo complete decomposition? (Relative atomic masses: O = 16.0, l = 35.5, K = 39.1) 3.20 g 6.40 g 9.60 g 19.2 g 22

23 64,, X and Y represent four different compounds. and react according to the following equation: + 2 2X + Y a grams of react with b grams of to give x grams of X and y grams of Y. What is the value of y? a + b x a + 2b x a + b 2x a + 2b 2x 2 65 Upon heating, a hydrogencarbonate XHO 3 decomposes according to the following equation: 2XHO 3 (s) X 2 O 3 (s) + H 2 O(l) + O 2 (g) sample of 1.50 g of XHO 3 is heated g of carbon dioxide is produced. What is the formula mass of XHO 3? (Relative atomic masses: = 12.0, O = 16.0) The oxide of metal M, M 2 O, can be reduced by passing hydrogen gas over the heated oxide. omplete reduction of 23.2 g of the oxide produces metal M and 1.80 g of water. What is the relative atomic mass of M? (Relative atomic masses: H = 1.0, O = 16.0) g of copper were added to excess silver nitrate solution. fter some time, the silver obtained is filtered off from the resulting solution. (Relative atomic masses: u = 63.5, g = 107.9) The final mass of the silver obtained would be less than 5 g. 5 g. 10 g. more than 10 g. 68 When a 1.00 g sample of limestone was dissolved in dilute hydrochloric acid completely, g of carbon dioxide was generated. What was the percentage by mass of calcium carbonate in the limestone? (Relative atomic masses: = 12.0, O = 16.0, a = 40.1) 16.7% 51.5% 64.7% 86.5% 69 When the iron ore pyrite, FeS 2, is roasted, iron(iii) oxide is produced. 4FeS 2 (s) + 11O 2 (g) 2Fe 2 O 3 (s) + 8SO 2 (g) Roasting 60.0 tonnes of the ore produces 36.7 tonnes of iron(iii) oxide. What is the percentage by mass of FeS 2 in the ore? (Relative atomic masses: O = 16.0, S = 32.1, Fe = 55.8; 1 tonne = 10 6 g) 27.6% 46.0% 55.2% 92.0% 70 When equal masses of magnesium and iron react separately with excess hydrochloric acid, magnesium gives more hydrogen than iron does. Which of the following deductions is correct? The metallic bond in magnesium is weaker than that in iron. The reactivity of magnesium is higher than that of iron. The atomic number of magnesium is greater than that of iron. The relative atomic mass of magnesium is smaller than that of iron. Part Unit 12 23

24 Part Unit Sulphur dioxide is produced when sulphur burns in oxygen. S(s) + O 2 (g) SO 2 (g) 48.2 g of sulphur burn in 64.0 g of oxygen. One of the reactants is in excess. What is the mass of sulphur dioxide produced? (Relative atomic masses: O = 16.0, S = 32.1) 96.2 g 112 g 128 g 144 g 72 Hydrazine (N 2 H 4 ) is used as rocket fuel. It reacts with oxygen according to the following equation: N 2 H 4 (l) + O 2 (g) N 2 (g) + 2H 2 O(l) In a particular rocket engine, 2.40 g of hydrazine and 3.40 g of oxygen are allowed to react. What is the mass of water produced? (Relative atomic masses: H = 1.0, N = 14.0, O = 16.0) 1.35 g 1.90 g 2.70 g 3.80 g 73 mmonia is manufactured from hydrogen and nitrogen by the following process: 3H 2 (g) + N 2 (g) 2NH 3 (g) In a certain experiment, 80 g of ammonia were produced from 60 g of hydrogen and excess nitrogen. What is the percentage yield of ammonia? (Relative atomic masses: H = 1.0, N = 14.0) 74 In the combustion of a certain fuel, 16.0 g of carbon dioxide are produced. This represents a 75.0% yield. What is the theoretical yield of carbon dioxide? 12.0 g 21.3 g 32.0 g 44.3 g 75 When copper is heated with excess sulphur, copper(i) sulphide is formed according to the following equation: 2u(s) + S(s) u 2 S(s) In a particular experiment, 2.40 g of copper were heated with excess sulphur to obtain 2.85 g of copper(i) sulphide. What is the percentage yield of copper(i) sulphide? (Relative atomic masses: S = 32.1, u = 63.5) 80.7% 84.7% 90.7% 94.7% 76 The molecular formula of ozone is O 3. Which of the following statements concerning 1 mole of ozone is / are correct? (vogadro constant = 6.02 x mol 1 ) (1) It contains 3 x 6.02 x atoms. (2) It contains 3 moles of molecules. (3) It contains the same number of atoms as 1 mole of O 2 (g). (1) only (2) only (1) and (3) only (2) and (3) only x 100% x 100% x 100% x 100% 24

25 77 Which of the following statements concerning 1 mole of magnesium is / are correct? (vogadro constant = 6.02 x mol 1 ; relative atomic mass: Mg = 24.3) (1) It can form 1 mole of Mg 2+ ions. (2) It can form 2 x 6.02 x Mg 2+ ions. (3) The mass of 1 mole of Mg 2+ ions is 48.6 g. (1) only (2) only (1) and (3) only (2) and (3) only 80 Which of the following contains the same number of atoms as 5.10 g of ammonia? (1) 17.6 g of carbon dioxide (2) 18.0 g of nitrogen monoxide (3) 42.6 g of chlorine (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0, l = 35.5) (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 78 The relative atomic masses of carbon and oxygen are 12.0 and 16.0 respectively. Which of the following statements concerning 88.0 g of carbon dioxide is / are correct? (vogadro constant = 6.02 x mol 1 ) (1) It contains 4 moles of oxygen atoms. (2) It contains 2 x 6.02 x atoms. (3) It contains 6 x 6.02 x molecules. (1) only (2) only (1) and (3) only (2) and (3) only Unit 13 orrosion of metals and their protection Fill in the blanks 1 The reaction of a metal with oxygen in the air, moisture or other substances in the environment is called corrosion. 2 The corrosion of iron is called rusting. The chemical name of rust is hydrated iron(iii) oxide. Part Unit g of sulphur and 1 g of oxygen contain the same number of atoms. Which of the following statements is / are correct? (1) The number of atoms in one mole of sulphur atoms is twice that in one mole of oxygen atoms. (2) The mass of one mole of sulphur atoms is twice that of one mole of oxygen atoms. (3) The number of occupied electron shells in a sulphur atom is twice that in an oxygen atom. (1) only (2) only (1) and (3) only (2) and (3) only 3 For rusting to occur, oxygen and water must be present. 4 Iron coated with zinc is called galvanized iron. 5 thin layer of metal can be plated on iron by an electrical process called electroplating. 6 To prevent iron from rusting, a piece of more reactive metal can be attached to it. This method is called sacrificial protection. 7 n underground pipeline is protected by joining a piece of magnesium or zinc to it. 25

26 8 car body is protected from rusting by connecting it to the negative terminal of the car battery. This method is called impressed current cathodic protection. 20 n underground pipeline can be protected T by joining a piece of magnesium to it. 21 Iron coated with zinc is used to make F cans for drinks. Part Unit 13 9 Stainless steel is an alloy of iron containing chromium and nickel. 10 The thickness of an aluminium oxide layer can be increased by a process called aluminium anodization. True or false ecide whether each of the following statements is true or false. 11 The chemical name of rust is hydrated F iron(ii) oxide. 12 For rusting to occur, oxygen and water T must be present. 13 n industrial environment speeds up T the rusting of iron. 14 The rusting process speeds up if the iron T is in contact with a less reactive metal. 22 Steel structures of a pier can be protected F from rusting by impressed current anodic protection. 23 When iron reacts with oxygen in the air, F an even coating of oxide forms and protects the metal beneath from further attack. 24 luminium anodization can increase the F strength of aluminium. 25 nodized aluminium is an alloy. F Multiple choice questions 26 There are green patches on the surface of the Statue of Liberty in the United States. The statue may contain copper. silver. tin. zinc. 15 Rusting occurs more slowly where the F iron surface is scratched. 27 Which iron nail in the test tubes shown below will rust most slowly? 16 Painting can protect iron from rusting. T 17 Tin protects iron from rusting by F sacrificial protection. 18 Food cans are usually made of mild steel T coated with tin. 19 When part of the zinc plated on an iron F object is scratched, the exposed iron rusts more quickly. 26

27 28 Rusting is speeded up by a high temperature because oxygen is present in greater amount. water is present in greater amount. the reaction goes faster. both oxygen and water are present in greater amount. 29 In which of the following cases will the iron nail rust most after 1 week? 31 n iron nail is covered with water. Which of the following procedures would NOT increase the rate at which the iron nail rusts? dding some sodium sulphate to the water dding some glucose to the water ttaching a copper wire to the nail Passing carbon dioxide through the water 32 Two experiments are set-up to study the rusting of iron nails. fter a short time, a blue colour will appear at 30 In which of the following cases will the iron nail rust most rapidly? both X and Y. neither X nor Y. X but not at Y. Y but not at X. irections: Questions 33 and 34 refer to the following experiment. The iron nails in the following glass dishes were wrapped with different metal strips. rust indicator solution containing potassium hexacyanoferrate(iii) and phenolphthalein was poured into the dishes to cover the nails. Part Unit 13 27

28 Part Unit In dish 1, which of the following colours would develop around the iron nail and the copper strip? Iron nail opper strip lue no colour lue pink Pink blue Pink no colour 34 In which of the dishes would the iron nail rust? ish 1 only ish 2 only ish 1 and ish 3 only ish 2 and ish 4 only 35 Tin-plating can be used to prevent the rusting of iron because tin is more lustrous than iron. tin is more reactive than iron and corrodes first. tin protects the iron from oxygen and water. tin and iron form an alloy which does not corrode. 36 Tin-plating, rather than zinc plating, is used to prevent the rusting of food cans because zinc corrodes more readily than tin. zinc is more expensive than tin. zinc is denser than tin. zinc ions are poisonous while tin ions are not. 37 Which of the following is the most suitable method for rust prevention in medical instruments? Painting Sacrificial protection Using stainless steel Tin plating 38 Which of the following methods is the most suitable for preventing the chain of a bicycle from rusting? oating with grease oating with plastic Painting Sacrificial protection 39 Which of the following combinations is correct? Iron article oat hanger Food can Underground water pipe ar body Method to prevent iron from rusting greasing galvanization joining a piece of lead to it connecting to the negative terminal of car battery 40 Which of the following methods NNOT prevent iron from rusting? Joining a copper block to iron oating iron with plastic oating iron with chromium Using an alloy of iron containing chromium and nickel 41 The corrosion of aluminium in the air quickly stops after the reaction starts because aluminium is unreactive. the oxide layer allows only oxygen to pass through. aluminium forms an alloy which does not corrode. the oxide layer protects the metal from further attack. 28

29 42 The corrosion resistance of aluminium can be increased by anodization because during the process, the strength of aluminium is increased. the pores in the aluminium oxide on the metal surface are covered. the aluminium oxide on the metal surface is changed to aluminium. the thickness of the aluminium oxide on the metal surface is increased. 43 The diagram below shows the experimental setup for aluminium anodization. 44 Which of the following statements concerning the rusting of iron is / are correct? (1) The chemical formula of rust is FeO xh 2 O. (2) ir and water must be present for the process to occur. (3) The rust is firmly attached to the iron surface and protects the metal underneath. (1) only (2) only (1) and (3) only (2) and (3) only 45 In which of the following cases will the iron nail rust after 1 week? Which of the following combinations is correct? Positive Negative electrode electrode Electrolyte luminium aluminium water object sheet luminium aluminium dilute object sheet sulphuric acid luminium aluminium dilute sheet object sulphuric acid luminium aluminium water sheet object (1) (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) (2) (3) 46 Rusting of a piece of iron will be speeded by (1) the presence of ionic substances. (2) scratching the surface of the iron. (3) attaching to tin. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) Part Unit 13 29

30 Part Unit Which of the following methods are used to protect iron from rusting? (1) nodization (2) hromium plating (3) Impressed current cathodic protection (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 48 Which of the following are advantages of anodizing aluminium? (1) It enables aluminium to be dyed readily. (2) It makes aluminium stronger. (3) It increases the corrosion resistance of aluminium. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) irections : 49 Which of the following statements correctly describe(s) the advantage(s) of using aluminium over iron to make window frames? (1) luminium is stronger than iron. (2) luminium is more corrosion resistant than iron. (3) luminium is cheaper than iron. (1) only (2) only (1) and (3) only (2) and (3) only 50 Which of the following substances are alloys? (1) nodized aluminium (2) ronze (3) 18-carat gold (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) Each question (Questions 51 55) consists of two separate statements. ecide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from to according to the following table : oth statements are true and the 2nd statement is a correct explanation of the 1st statement. oth statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. The 1st statement is false but the 2nd statement is true. oth statements are false. 1st statement 2nd statement 51 Hot water iron pipes rust more quickly than higher temperature speeds up the rusting cold water iron pipes. process. 52 Galvanized iron is used for making food cans. Tin can prevent iron from rusting by sacrificial protection. 53 Steel structures of a pier may be protected from uring the process, iron reacts with oxygen rusting by impressed current anodic protection. to form an even coating of oxide on the surface. 54 Stainless steel is seldom used to make large Stainless steel contains chromium. structures nodization is a method used to increase the y anodization, an oxide layer is formed to strength of aluminium. protect the aluminium.

31 Part Topic-based exercise Multiple choice questions 1 Which of the following metals is the most abundant in the Earth s crust? luminium alcium Iron Magnesium 5 The diagram shows the arrangement of the atoms in pure copper. 2 Which of the following properties is considered the most important one when choosing an alloy for making fuse in electric plugs? Low melting point High electrical conductivity Good malleability Good strength 3 Which of the following combinations is INORRET? Metal Use opper making duralumin Lead making solder Titanium making railings Zinc making dry cells irections: Questions 4 6 refer to copper and zinc. 4 opper and zinc can be extracted from their oxides by strongly heating the oxides with carbon. In these reactions, the oxides are oxidized. distilled. reduced. combined. opper can be made harder by mixing it with zinc. This is because the copper atoms cannot now easily slide over each other. the zinc atoms attach themselves strongly to the copper atoms. the zinc atoms form strong bonds with the copper atoms. zinc is harder than copper. 6 There are a lot of researches on new ways of extracting copper from low-grade ores. One reason for this is a significant rise in the price of copper. more copper ore is being found. a reduction in the use of copper. low-grade ores contain more copper. 7 The ancient people discovered copper, but not aluminium because aluminium is very rare. aluminium is difficult to extract. aluminium is light. aluminium is found very deep in the Earth s crust. Part 31

32 Part 32 8 onsider the following experiment. The metal could NOT be aluminium. iron. lead. zinc. 9 In which of the following experiments will a reaction take place? dding aluminium to water dding copper to dilute sulphuric acid dding mercury to dilute hydrochloric acid Heating zinc in air 10 cold water tank starts to react when some dilute sulphuric acid is accidentally poured into it. The tank could be made of calcium. copper. potassium. zinc. 11 X, Y and Z are three different metals. The following table shows the results of two experiments. Experiment dding the metal to water Metal X Y Z no observable change Heating the a solid with metal oxide with metallic lustre carbon powder formed no observable change no observable change gas bubbles given off no observable change Which of the following arrangements represents the order of increasing reactivity of the three metals? X < Y < Z X < Z < Y Y < X < Z Z < X < Y irections: Questions refer to the following descriptions of three different metals, X, Y and Z. X and Y can react with cold water to give hydrogen. Z can react with dilute hydrochloric acid but not water. Only Y is stored in paraffin oil in the laboratory. 12 The order of decreasing reactivity of the metals is Z > X > Y. X > Y > Z. Y > X > Z. Z > Y > X. 13 X could be l. a. u. Zn. 14 ifferent metals are dropped into water or dilute hydrochloric acid. ssuming that the experimental conditions are the same, which of the following comparisons concerning the initial rates of hydrogen formation is correct? Initial rate of hydrogen formation Initial rate of hydrogen formation Mg and H 2 O > a and Hl Fe and Hl > K and H 2 O K and H 2 O > Rb and H 2 O Rb and Hl > Mg and Hl 15 X and Y are two different metals. Which of the following shows that Y is more reactive than X? X is stored in paraffin oil while Y is not. X reacts with dilute hydrochloric acid but Y does not. X is a Group I element while Y is a Group II element. The oxide of X gives X when heated with carbon while the oxide of Y does not.

33 16 onsider the following equation: xh 2 + Fe 3 O 4 yfe + zh 2 O Which of the following combinations is correct? x y z qua-regia, a mixture of nitric acid and hydrochloric acid, can dissolve gold. The equation for the reaction is shown below: u + whno 3 + xhl Hul 4 + yh 2 O + zno 2 Which of the following combinations is correct? w x y z onsider the following equation: 5H 2 S(g) + 2KMnO 4 (s) + 3H 2 SO 4 (aq) 5S(x) + 8H 2 O(y) + K 2 SO 4 (z) + 2MnSO 4 (aq) Which of the following combinations is correct? x y z s aq l s l aq aq aq l aq l aq irections: Questions 19 and 20 refer to the following experiment. 19 X is probably iron. magnesium. silver. zinc. 20 What is the colour change of the solution in the test tube? The solution remains colourless. The solution changes from colourless to greenish blue. The solution changes from colourless to pale green. The solution changes from blue to pale blue. 21 In which of the following cases will a reaction take place? 22 gardener uses a compound that NNOT be stored in a zinc-plated watering can. The compound could be a(no 3 ) 2. uso 4. MgSO 4. KNO 3. Part student placed a piece of copper into a test tube containing a solution of the nitrate of metal X. grey mud-like deposit formed on the copper. 23 What would happen when magnesium is added to a solution containing zinc nitrate and calcium nitrate? No deposit forms. deposit of zinc forms. deposit of calcium forms. eposits of both calcium and zinc form. 33

34 24 X and Z are two different metals. X reacts with the solution of sulphate of Z according to the following equation: X(s) + Z 2+ (aq) X 2+ (aq) + Z(s) Which of the following deductions is correct? oth X and Z can react with dilute hydrochloric acid. oth X and Z are Group II elements. Z is more reactive than X. toms of X lose electrons to form cations more readily when compared with atoms of Z. 25 The year of discovery of a metal is closely related to the 27 What is the number of moles of ions in 1 mole of chromium(iii) sulphate? mixture of sodium chloride and sodium sulphate is known to contain 4 moles of chloride ions and 3 moles of sulphate ions. How many moles of sodium ions are present in the mixture? Part abundance of the metal in the Earth s crust. relative atomic mass of the metal. melting point of the oxide of the metal. position of the metal in the reactivity series. 26 X, Y and Z are three different metals. The table below shows the observations when each of them is put into silver nitrate solution: Metal X Observation a grey deposit formed on the metal 29 Which of the following has the greatest number of ions? 4 moles of iron(iii) sulphate 5 moles of calcium phosphate 6 moles of barium hydrogencarbonate 7 moles of magnesium hydroxide 30 certain form of carbon is composed of 60 molecules. Each 60 molecule is formed by 60 carbon atoms bonded together like a football as shown in the diagram below: Y Z a grey deposit formed on the metal and a colourless gas evolved no observable change Which of the following arrangements correctly represents the descending order of reactivity of the metals? X > Y > Z Y > X > Z Y > Z > X Z > X > Y pproximate how many such molecules are present in 12 g of this form of carbon? (Relative atomic mass: = 12.0; vogadro constant = 6.02 x mol 1 ) 1.0 x x x x

35 31 How many moles of glucose ( 6 H 12 O 6 ) contain x oxygen atoms? (L represents the vogadro constant.) x L L x x 6L 6x L 32 The chemical formulae of two chlorine oxides are l 2 O and l 2 O 7. If 1 mole of l 2 O contains n atoms, 2 moles of l 2 O 7 would contain 7 2 n atoms. 2n atoms. 4n atoms. 6n atoms. 33 The relative atomic masses of hydrogen and oxygen are 1.0 and 16.0 respectively. Which of the following statements concerning 54.0 g of water is correct? (vogadro constant = 6.02 x mol 1 ) It contains 9 moles of molecules. It contains 3 x 6.02 x atoms. It contains 6 moles of hydrogen atoms. It contains 6 x 6.02 x oxygen atoms. 34 two carat diamond used in a ring contains 2 x carbon atoms. What is the approximate mass of the diamond? (Relative atomic mass: = 12.0; vogadro constant = 6.02 x mol 1 ) 0.10 g 0.20 g 0.40 g 0.80 g 35 Which of the following contains the same number of atoms as 6.41 g of sulphur dioxide? (Relative atomic masses: H = 1.0, = 12.0, N = 14.0, O = 16.0, S = 32.1, l = 35.5) 1.70 g of ammonia 2.20 g of carbon dioxide 3.65 g of hydrogen chloride 4.60 g of nitrogen dioxide 36 The molecular formula of an element X is X 2. If the vogadro constant is L mol 1, how many molecules are there in 76.0 g of the element? (Relative atomic mass of X = 19.0) 1 2 L L 2L 3L 37 Which of the following gases contains the SMLLEST number of molecules? (Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, F = 19.0) 100 g of fluorine 100 g of nitrogen 100 g of oxygen 100 g of hydrogen 38 The formula of hydrated iron(ii) sulphate is FeSO 4 xh 2 O. On strong heating, 18.1 g of the hydrated sulphate produces 8.20 g of water. What is the value of x? (Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, Fe = 55.8) Part 35

36 39 The relative atomic mass of element X is It forms an oxide containing 18.4% of oxygen by mass. What is the mole ratio of X to oxygen in the oxide? (Relative atomic mass: O = 16.0) 1 : 2 1 : 3 2 : 1 2 : 3 40 Metal M forms an oxide. omplete reduction of 11.9 g of this oxide by carbon produces metal M and 3.29 g of carbon dioxide. What is the empirical formula of the oxide? (Relative atomic masses: = 12.0, O = 16.0, M = 63.5) 43 car airbag contains sodium azide (NaN 3 ) and potassium nitrate. Sodium azide decomposes according to the following equation: 2NaN 3 (s) 2Na(s) + 3N 2 (g) The sodium produced reacts immediately with potassium nitrate producing more nitrogen. 10Na(s) + 2KNO 3 (s) N 2 (g) + 5Na 2 O(s) + K 2 O(s) What is the total number of moles of nitrogen produced by 1.00 mole of sodium azide in this sequence? 1.20 moles 1.50 moles 1.60 moles 4.00 moles Part M 2 O MO MO 2 M 2 O 3 41 Rhodonite is a decorative stone that consists mainly of pink MnSiO 3. Less valuable variants of the stones have black streaks of MnO 2 in them. nalysis of a particular sample of rhodonite indicates that it contains a total of 49.2% of Mn by mass. What is the percentage by mass of MnO 2 in the sample? (Relative atomic mass: Mn = 54.9; formula masses: MnSiO 3 = 131.0, MnO 2 = 86.9) 34.3% 44.6% 55.4% 63.5% 42 The relative atomic mass of metal X is g of X are allowed to react with excess oxygen until completely oxidized g of oxide are obtained. What is the empirical formula of the oxide? (Relative atomic mass: O = 16.0) XO X 2 O 3 X 3 O 2 X 3 O 4 44 P, Q, R and S represent four different compounds. P and Q react according to the following equation: 2P + Q R + 2S p grams of P react with q grams of Q to give r grams of R and s grams of S. What is the value of s? p + q r 2p + q r 2(p + q r) 2p + q r 2 45 Upon heating, calcium nitrate decomposes according to the following equation: 2a(NO 3 ) 2 (s) 2aO(s) + 4NO 2 (g) + O 2 (g) sample of 82.0 g of calcium nitrate is heated strongly. What is the mass of oxygen obtained? (Relative atomic masses: N = 14.0, O = 16.0, a = 40.1) 8.00 g 12.0 g 16.0 g 20.0 g 36

37 46 Lithium hydroxide can absorb carbon dioxide. The reaction can be represented by the following equation: 2LiOH(s) + O 2 (g) Li 2 O 3 (s) + H 2 O(l) What is the mass of lithium hydroxide needed for absorbing 11.0 g of carbon dioxide? (Relative atomic masses: H = 1.0, Li = 6.9, = 12.0, O = 16.0) 5.98 g 12.0 g 17.9 g 23.9 g 47 NaHO 3 decomposes upon heating to form Na 2 O 3, O 2 and H 2 O. What is the mass of Na 2 O 3 formed if 33.6 g of NaHO 3 undergo complete decomposition? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, Na = 23.0) 5.30 g 10.6 g 21.2 g 42.4 g 48 Metal M forms an oxide in which the ion of M carries +2 charge. omplete reduction of 13.4 g of this oxide by hydrogen gas produces metal M and 1.08 g of water. What is the relative atomic mass of M? (Relative atomic masses: H = 1.0, O = 16.0) arbon dioxide and hydrogen react to produce methanol (H 3 OH) according to the following equation: O 2 (g) + 3H 2 (g) H 3 OH(g) + H 2 O(g) In an experiment, 6.60 g of carbon dioxide are allowed to react with 1.20 g of hydrogen. What is the mass of H 3 OH obtained? (Relative atomic masses: H = 1.0, = 12.0, O = 16.0) 2.60 g 3.20 g 4.80 g 6.40 g 50 onsider the reaction between ammonia and copper(ii) oxide: 2NH 3 (g) + 3uO(s) N 2 (g) + 3H 2 O(l) + 3u(s) In an experiment, 6.80 g of ammonia are allowed to react with 35.8 g of copper(ii) oxide. What is the mass of nitrogen obtained? (Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, u = 63.5) 2.80 g 4.20 g 5.60 g 8.40 g 51 luminium reacts with chlorine according to the following equation: 2l(s) + 3l 2 (g) 2ll 3 (s) In a certain experiment, 8.10 g of aluminium were heated with excess chlorine g of aluminium chloride were obtained. What is the percentage yield of aluminium chloride? (Relative atomic masses: l = 27.0, l = 35.5) 36.6% 55.3% 73.6% 95.3% g of an impure sample of silver oxide (g 2 O) is heated strongly g of silver are obtained. What is the percentage by mass of g 2 O in the sample? (Relative atomic masses: O = 16.0, g = 107.9) 53.5% 77.1% 87.1% 93.5% Part 37

38 Part 53 solid mixture consists of 1.0 mole of calcium carbonate and 1.0 mole of sodium carbonate. What is the number of moles of hydrochloric acid required to liberate all the carbon dioxide from the mixture? 1.5 moles 2.0 moles 3.0 moles 4.0 moles 54 Metal X reacts with dilute sulphuric acid according to the following equation: X(s) + 2H + (aq) X 2+ (aq) + H 2 (g) When equal masses of X and zinc are added separately to excess dilute sulphuric acid, X gives more hydrogen than zinc does. Which of the following deductions is correct? The reactivity of X is higher than that of zinc. The density of X is smaller than that of zinc. The atomic number of X is greater than that of zinc. The relative atomic mass of X is smaller than that of zinc. 55 When 100 g of PURE calcium carbonate (formula mass = 100.1) reacted with excess hydrochloric acid, 44 g of carbon dioxide were obtained. However, in a similar experiment using 100 g of IMPURE calcium carbonate, 46 g of carbon dioxide were obtained. ssuming that the impurity is a metallic carbonate, what would this impurity be? (Formula masses: MgO 3 = 84.3, ZnO 3 = 125.4, FeO 3 = 115.8, ao 3 = 197.3) MgO 3 ZnO 3 FeO 3 ao 3 56 In which of the following cases will the iron nail rust most rapidly? 57 In which of the following cases will the rusting of iron nail be FSTEST? 58 Which of the following combinations is INORRET? Iron article ath tap Fence oor hinge Ship s hull Method to prevent iron from rusting chromium-plating painting galvanization sacrificial protection 38

39 59 Zinc foil reacts readily with dilute sulphuric acid, but a piece of household aluminium foil does not. Which of the following is a correct explanation? Zinc is above aluminium in the reactivity series. luminium sulphate is insoluble in water and thus prevents any further reaction once it is formed. Household aluminium foil is actually made of nickel. luminium foil is always coated with an oxide layer. 60 Which of the following combinations concerning the uses of metals are correct? Metal Use (1) admium making rechargeable cells (2) hromium making stainless steel (3) Titanium making supersonic aircraft (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 61 Titanium is commonly used to make replacement hip joints because (1) its density is high. (2) it can resist corrosion. (3) it is biocompatible. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 62 rass is commonly used to make ornaments because (1) it has an attractive appearance. (2) it can resist corrosion. (3) it is stronger than pure copper. (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 63 small piece of sodium is dropped into a trough of water containing universal indicator. Which of the following observations is / are correct? (1) Sodium moves rapidly on the water surface. (2) Sodium dissolves in water and the solution turns red. (3) Sodium burns with a lilac flame. (1) only (2) only (1) and (3) only (2) and (3) only 64 In which of the following experiments will a gas be produced? (1) Heating magnesium carbonate strongly (2) dding iron to dilute sulphuric acid (3) dding copper to dilute hydrochloric acid (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 65 The name of iron pyrite is fool s gold. Which of the following methods can be used to distinguish iron pyrite from gold? (1) omparing their hardness (2) omparing their malleability (3) omparing the effect of heat on them (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 66 Magnesium can be obtained from magesium oxide by (1) electrolysis of the molten oxide. (2) heating the oxide with carbon. (3) heating the oxide with zinc powder. (1) only (2) only (1) and (3) only (2) and (3) only Part 39

40 Part 67 Metal X is slightly more reactive than iron. Which of the following statements concerning X is / are probably correct? (1) X remains shiny after exposed to air for a period of time. (2) X reacts readily with dilute hydrochloric acid. (3) X can be extracted from its oxide by carbon reduction at the temperature of unsen flame. (1) only (2) only (1) and (3) only (2) and (3) only 68 From which of the following processes can copper be obtained? (1) dding silver to dilute copper(ii) sulphate solution (2) Heating copper(ii) oxide with magnesium powder (3) Mixing copper(ii) oxide with carbon (1) only (2) only (1) and (3) only (2) and (3) only 69 Which of the following statements concerning 1 mole of aluminium is / are correct? (vogadro constant = 6.02 x mol 1 ) (1) It can form 1 mole of l 3+ ions. (2) It can form 3 x 6.02 x l 3+ ions. (3) It contains the same number of atoms as 3 moles of sodium. (1) only (2) only (1) and (3) only (2) and (3) only 70 The relative atomic mass of hydrogen and oxygen are 1.0 and 16.0 respectively. Which of the following statements concerning 36.0 g of water is / are correct? (vogadro constant = 6.02 x mol 1 ) (1) It contains 3 x 6.02 x molecules. (2) It contains 6 x 6.02 x atoms. (3) It contains 2 moles of hydrogen atoms. (1) only (2) only (1) and (3) only (2) and (3) only 71 Which of the following iron nails will rust after a few days? (1) (2) (1) only (2) only (1) and (3) only (2) and (3) only (3) 72 Which of the following methods are usually used to prevent a car body from rusting? (1) pply a layer of grease on the car body (2) onnect the car body to the car battery (3) pply a layer of paint on the car body (1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3) 40

41 irections : Each question (Questions 73 80) consists of two separate statements. ecide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from to according to the following table : oth statements are true and the 2nd statement is a correct explanation of the 1st statement. oth statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. The 1st statement is false but the 2nd statement is true. oth statements are false. 1st statement 2nd statement 73 car is not easy to recycle. car is made of different metals. 74 Iron was used earlier than copper in the history. Iron is more abundant than copper in the Earth s crust. 75 When equal masses of a and Zn are added a atoms lose electrons more readily than Zn separately to excess dilute Hl, a greater amount atoms. of gas will be produced by a than Zn. 76 When equal masses of Li and Na are added Na is more reactive than Li. separately to water, a greater amount of gas will be produced by Na than Li. Part 77 opper can displace silver from silver nitrate opper can form an ion with a charge of +2 solution. while silver can form an ion with a charge of mole of O 3 (g) contains more molecules than The number of atoms in 1 mole of O 3 (g) is 1 mole of O 2 (g). greater than that in 1 mole of O 2 (g). 79 Iron gratings near seaside corrode more quickly. Sodium chloride in the air speeds up corrosion. 80 Painting is often used to protect the moving Painting is a cheap method of protecting iron parts of machine from rusting. from rusting. 41

42 Short questions 81 The table below shows information about four different metals,, and. Metal ost orrosion resistance Heat conductivity Mechanical strength ensity low low medium medium low high high good high high low medium medium high medium medium medium good medium medium Suggest a metal that is the most suitable for making each of the following articles. State TWO reasons for your choice in each case. a) medal (3 marks) (1) ny two of the following: High corrosion resistance (1) / high mechanical strength (1) / high density (1) b) gate (3 marks) Part (1) ny two of the following: Low cost (1) / high mechanical strength (1) / medium density (1) c) The metal base of a hot pot (3 marks) (1) Medium price (1) Good conductivity of heat (1) 82 Write a chemical equation for each of the following reactions: a) Magnesium burns in air 2Mg(s) + O 2 (g) 2MgO(s) (1) b) luminium burns in air 4l(s) + 3O 2 (g) 2l 2 O 3 (s) (1) c) Sodium reacts with water 2Na(s) + 2H 2 O(l) 2NaOH(aq) + H 2 (g) (1) 42

43 d) Zinc reacts with steam Zn(s) + H 2 O(g) ZnO(s) + H 2 (g) (1) e) alcium reacts with dilute hydrochloric acid a(s) + 2Hl(aq) al 2 (aq) + H 2 (g) (1) f) Silver oxide decomposes upon heating 2g 2 O(s) 4g(s) + O 2 (g) (1) g) arbon removes oxygen from copper(ii) oxide upon heating 2uO(s) + (s) 2u(s) + O 2 (g) (1) h) luminium removes oxygen from iron(iii) oxide upon ignition Fe 2 O 3 (s) + 2l(s) 2Fe(s) + l 2 O 3 (s) (1) 83 Write an ionic equation for each of the following reactions: a) Magnesium + dilute hydrochloric acid Mg(s) + 2H + (aq) Mg 2+ (aq) + H 2 (g) (1) b) Zinc + dilute sulphuric acid Zn(s) + 2H + (aq) Zn 2+ (aq) + H 2 (g) (1) c) Iron + copper(ii) sulphate solution Fe(s) + u 2+ (aq) Fe 2+ (aq) + u(s) (1) Part d) opper + silver nitrate solution u(s) + 2g + (aq) u 2+ (aq) + 2g(s) (1) 84 For each of the following experiments, state ONE expected observation and write a chemical equation for the reaction involved. a) urning sodium in air (2 marks) Sodium burns vigorously with a golden yellow flame. / white smoke forms. (1) 4Na(s) + O 2 (g) 2Na 2 O(s) (1) b) dding magnesium to dilute sulphuric acid (2 marks) Gas bubbles are given off. / Magnesium dissolves in the acid. (1) Mg(s) + H 2 SO 4 (aq) MgSO 4 (aq) + H 2 (g) (1) 43

44 c) ropping potassium into water (2 marks) Potassium melts to form a silvery bead. / The bead moves rapidly on the water surface. / Potassium burns with a lilac flame. (1) 2K(s) + 2H 2 O(l) 2KOH(aq) + H 2 (g) (1) d) urning calcium in air (2 marks) alcium burns with a brick-red flame. / white powder forms. (1) 2a(s) + O 2 (g) 2aO(s) (1) e) ropping calcium into water (2 marks) alcium sinks in water. / steady steam of bubbles forms. / The water becomes milky. (1) a(s) + 2H 2 O(l) a(oh) 2 (s) + H 2 (g) (1) f) ipping zinc into copper(ii) sulphate solution (2 marks) The zinc metal slowly becomes coated with a brown layer. / The blue colour of the solution fades gradually. (1) Zn(s) + uso 4 (aq) ZnSO 4 (aq) + u(s) (1) 85 omplete the following table. (12 marks) Part Substance Mass of substance present (g) Molar mass of substance (g mol 1 ) Number of moles of substance present (mol) Water H 2 O 117 (1) 18.0 (1) 6.50 Iron(III) oxide Fe 2 O (1) (1) 4.00 (1) Potassium carbonate K 2 O (1) 2.50 (1) arbon dioxide O (1) 1.40 (1) Number of particles present 3.91 x molecules (1) 2.41 x formula units 1.51 x formula units (1) 8.43 x molecules (1) (Relative atomic masses: H = 1.0, = 12.0, O = 16.0, K = 39.1, Fe = 55.8; vogadro constant = 6.02 x mol 1 ) 44

45 Structured questions 86 Many everyday items are made from iron. a) Haematite is an ore of iron. Haematite contains iron(iii) oxide. What is the meaning of the term ore? Rocks from which we obtain metals are called ores. (1) b) Iron can be produced by reacting iron(iii) oxide with carbon monoxide in a blast furnace. i) What type of reaction produces the iron? Reduction (1) ii) Write a chemical equation for the reaction involved. Fe 2 O 3 (s) + 3O(g) 2Fe(s) + 3O 2 (g) (1) c) Pure iron is relatively soft and not very strong. n iron alloy is prepared by adding another metal to iron. This alloy is much stronger than pure iron. Explain the difference in strength of pure iron and the iron alloy by referring to the diagrams. (3 marks) Part In pure iron, all the atoms are of the same size. Hence the layers of atoms are able to slide over each other easily. (1) In the iron alloy, larger metal atoms are present. They cause a distortion to the regular arrangement of the iron atoms. (1) So, it is difficult for the layers of atoms to slide over each other. (1) d) The diagram shows the way in which iron is extracted, used and recycled. 45

46 i) Explain why the recycling of iron is necessary for sustainable development. (3 marks) Metal resources can be saved. (1) Fuel can be saved. (1) Environmental impact due to metal waste and mining can be reduced. (1) ii) Suggest TWO problems associated with recycling. (2 marks) ny two of the following: The cost is high. (1) / It is difficult to get people to save metal waste. (1) / It is difficult to sort the metal waste. (1) 87 This following table shows the densities of two Group I metals. Metal ensity (g cm 3 ) Potassium (K) 0.86 Rubidium (Rb) 1.53 ensity of water = 1.0 g cm 3 Part a) i) Suggest TWO observable differences when potassium and rubidium are added separately into a trough of cold water. (2 marks) Rubidium sinks in water while potassium floats on water. (1) Rubidium reacts more vigorously than potassium. (1) ii) ccount for the differences. (3 marks) Rubidium is denser than water and potassium is less dense than water. (1) The outermost shell electron in a rubidium atom is further away from the nucleus than that in a potassium atom. There is less attraction between the nucleus and the outermost shell electron in a rubidium atom. (1) Hence a rubidium atom lose an electron more readily than a potassium atom. Therefore rubidium is more reactive than potassium. (1) iii) Write a chemical equation for the reaction between rubidium and water. 2Rb(s) + 2H 2 O(l) 2RbOH(aq) + H 2 (g) (1) 46

47 b) Rubidium is stored in paraffin oil in a bottle with suitable hazard warning labels. i) Why should rubidium be stored in paraffin oil? This prevents rubidium from reacting with moisture and oxygen in air. (1) ii) raw ONE hazard warning label which should appear on the bottle containing rubidium. Explosive or flammable (1) c) alcium also reacts with cold water. In a certain experiment, a student added some calcium granules into a beaker of cold water. i) Write a chemical equation for the reaction between calcium and water. a(s) + 2H 2 O(l) a(oh) 2 (s) + H 2 (g) (1) ii) raw a labelled diagram of the set-up for carrying out the reaction of calcium with cold water in a beaker, with the collection of the gaseous product. (2 marks) Part (1 mark for correct set-up; 1 mark for correct labels; 0 mark if the set-up is not workable) (2) iii) State TWO differences in observation when potassium and calcium are added separately to cold water. (2 marks) Potassium floats on water while calcium sinks. (1) Potassium burns with a lilac flame while calcium does not catch fire. (1) 88 The properties of three metals are given in the following table. Metal Reaction X Y Z Heating in air turns black a white powder forms (the a brick-red flame observed powder is yellow when hot) Reaction with cold water Reaction with dilute hydrochloric acid no observable change no observable change gas bubbles given off slowly no observable change gas bubbles given off readily gas bubbles given off vigorously ased on the information given above, answer the following questions. 47

48 a) rrange the three metals in descending order of reactivity. Explain your answer. (3 marks) Z > Y > X (1) Only Z reacts with cold water. Therefore it is the most reactive. (1) Y reacts with dilute hydrochloric acid but X shows no reaction with dilute hydrochloric acid. Therefore Y is more reactive than X. (1) b) i) Suggest what X might be. opper (1) ii) Will there be any reaction when its oxide is heated with carbon? Write an equation for the reaction, if any. (2 marks) X / copper is produced. (1) 2uO(s) + (s) 2u(s) + O 2 (g) (1) c) i) Suggest what Y might be. Zinc (1) Part ii) Write a chemical equation for the reaction between Y and dilute hydrochloric acid. Zn(s) + 2Hl(aq) Znl 2 (aq) + H 2 (g) (1) d) i) Suggest what Z might be. alcium (1) ii) What is the gas formed when Z is added to water? Suggest a test for the gas. (2 marks) Hydrogen (1) It gives a pop sound when tested with a burning splint. (1) iii) Write a chemical equation for the reaction between Z and water. a(s) + 2H 2 O(l) a(oh) 2 (s) + H 2 (g) (1) 48

49 iv) raw a labelled diagram of the set-up for carrying out the reaction between Z and cold water, with the collection of the gaseous product. (2 marks) (1 mark for correct set-up; 1 mark for correct labels; 0 mark if the set-up is not workable) (2) e) Predict whether X or Z was discovered earlier. Explain your answer. (2 marks) X was discovered earlier. (1) It is less reactive than Z and thus easier to extract. (1) 89 X, Y and Z are three different metals. The table below shows the results of two experiments carried out using the metals or their oxides. Metal Experiment X Y Z Reaction with steam no observable change a gas given off no observable change Heating the metal oxide no observable change no observable change a metal produced Part a) raw an experimental set-up for the reaction between a metal and steam, with the collection of the gaseous product. (3 marks) (1 mark for correct set-up; 1 mark for correct collection method for gaseous product; 1 mark for correct labels; 0 mark if the set-up is not workable) (3) 49

50 b) rrange the three metals in order of increasing reactivity. Explain your answer. (3 marks) Z < X < Y (1) Only the oxide of Z is decomposed by heating alone. Therefore Z is the least reactive. (1) Only Y can react with steam. Therefore it is the most reactive. (1) c) The oxide of Z has a chemical formula Z 2 O. i) Suggest what Z might be. Silver (1) ii) Write a chemical equation for the decomposition of the oxide of Z upon heating. 2g 2 O(s) 4g(s) + O 2 (g) or 2Z 2 O(s) 4Z(s) + O 2 (g) (1) iii) Would there be any reaction between copper and the solution of nitrate of Z? Write an ionic equation for the reaction, if any. (2 marks) Yes (1) u(s) + 2g + (aq) u 2+ (aq) + 2g(s) or u(s) + 2Z + (aq) u 2+ (aq) + 2Z(s) (1) Part d) The following table shows the year of discovery of the three metals. Metal Year of discovery X ancient Y 1746 Z ancient Suggest a relationship between the reactivity and the year of discovery of metals. Less reactive metals were discovered first and more reactive metals were discovered later. (1) 90 The results of experiments of three metals X, Y and Z are summarized in the following table: Metal Experiment X Y Z Reaction with cold water a gas given off no observable change no observable change Reaction with copper(ii) nitrate solution a gas given off and a reddish brown solid formed no observable change a reddish brown solid formed Heating metal oxide with carbon powder no observable change a solid with metallic lustre formed no observable change 50

51 a) What is the gas given off when X reacts with cold water? Suggest a test for the gas. (2 marks) Hydrogen (1) It gives a pop sound when tested with a burning splint. (1) b) rrange the three metals in order of increasing reactivity. Explain your answer. (3 marks) Y < Z < X (1) X and Z are more reactive than Y as both X and Z can displace copper from copper(ii) nitrate solution but Y cannot. Therefore Y is the least reactive. (or oxides of X and Z cannot be reduced by carbon but oxide of Y can.) (1) X is more reactive than Z as X can react with cold water but Z cannot. (1) c) Why is a gas formed when X is added to copper(ii) nitrate solution? (2 marks) X is a reactive metal. (1) It reacts with water in the copper(ii) nitrate solution and hydrogen is given off. (1) d) Z burns in air with a bright light. Part i) Suggest what Z might be. Magnesium (1) ii) Name the type of reaction that occurs when Z reacts with copper(ii) nitrate solution. isplacement reaction (1) iii) Suggest another observation when Z reacts with copper(ii) nitrate solution. The blue colour of the solution fades. (1) iv) Write an ionic equation for the reaction between Z and copper(ii) nitrate solution. Mg(s) + u 2+ (aq) Mg 2+ (aq) + u(s) or Z(s) + u 2+ (aq) Z 2+ (aq) + u(s) (1) 51

52 91 Results of some reactions of four metals,, and are shown below: Reaction Result (i) (s) + Hl(aq) (ii) (s) + Hl(aq) (iii) (s) + O 2 (g) (iv) (s) + O 2 (g) (v) (s) + H 2 O(g) (vi) (s) + H 2 O(g) no reaction reacts steadily to give hydrogen an oxide is formed when heated no reaction when heated reacts slowly with steam reacts vigorously with steam a) rrange the four metals in descending order of reactivity. Explain briefly. (4 marks) > > > (1) From reactions (v) and (vi), it can be concluded that is more reactive than because reacts vigorously with steam while reacts slowly with steam. (1) From reactions (i) and (ii), it can be concluded that is more reactive than because reacts with dilute hydrochloric acid but does not. (1) From reactions (iii) and (iv), it can be concluded that is more reactive than because oxide of is formed upon Part heating while there is no reaction for. (1) b) nother metal E reacts with dilute hydrochloric acid to give hydrogen. The solution of a compound of E also shows the following reaction: (s) + E 2+ (aq) 2+ (aq) + E(s) Where would you place E in the reactivity series among,, and? Explain briefly. (3 marks) E is more reactive than because E reacts with dilute hydrochloric acid but does not. (1) E is less reactive than because can displace E from a solution of compound of E. (1) Thus E should be placed between and in the reactivity series. (1) 52

53 c) In an oxide of metal, the ion of carries +2 charges. omplete reduction of 14.3 g of this oxide by hydrogen gas produces metal and 3.24 g of water. What is the relative atomic mass of? (Relative atomic masses: H = 1.0, O = 16.0) (3 marks) Let x be the relative atomic mass of. The chemical formula of the oxide of is O. O(s) + H 2 (g) (s) + H 2 O(l) Number of moles of H 2 O produced = mass of H 2 O molar mass of H 2 O = 3.24 g 18.0 g mol = mol 1 (1) ccording to the equation, 1 mole of O produces 1 mole of H 2 O. number of moles of O = mol mass of O = molar mass of O 14.3 g = (x ) g mol 1 (1) x = 63.4 (1) 92 Titanium can be extracted from titanium(iv) oxide (TiO 2 ). The extraction consists of two main steps: (s), l 2 (g) Step 1 TiO 2 (s) Til 4 (g) Part Step 2 Til 4 (g) Mg(l) Ti(s) a) esides titanium, magnesium chloride is also produced in Step 2. Write a chemical equation for the reaction involved. 2Mg(l) + Til 4 (g) Ti(s) + 2Mgl 2 (l) (1) b) ecide whether titanium or magnesium is more reactive. Explain your answer. (3 marks) Magnesium is more reactive than titanium. (1) Magnesium atoms lose electrons more easily. (1) In the reaction between Til 4 and Mg, magnesium competes for the chlorine and wins. (1) 53

54 c) In a certain experiment, 11.4 g of Til 4 were allowed to react with excess Mg g of Ti were obtained. What was the percentage yield of Ti? (Relative atomic masses: Mg = 24.3, l = 35.5, Ti = 47.9) mass of Til g Number of moles of Til 4 = = = mol molar mass of Til g mol 1 (3 marks) (1) ccording to the equation for the reaction between Til 4 and Mg, 1 mole of Til 4 produces 1 mole of Ti. number of moles of Ti obtained = mol Theoretical yield of Ti = number of moles of Ti x molar mass of Ti = mol x 47.9 g mol 1 = 2.87 g (1) Percentage yield of Ti = 2.54 g 2.87 g x 100% = 88.5% (1) d) i) State ONE use of titanium. Making supersonic aircraft (1) or making tooth implants / replacement hip joints (1) Part ii) Suggest TWO properties of titanium that make it suitable for the application stated in (i). (2 marks) ny two of the following: Light (1) / very strong (1) / very high melting point (1) / resists corrosion (1) OR Light (1) / very strong (1) / resists corrosion (1) / can be easily shaped (1) / biocompatible (1) 93 one consists of a complex mixture of calcium salts, such as calcium carbonate, and other materials. If bone is strongly heated, the calcium salts turn into calcium oxide. This can be separated from the other materials by dissolving it in dilute hydrochloric acid, forming calcium chloride solution. Water is also formed in the reaction. a) Write a chemical equation for the reaction between calcium oxide and dilute hydrochloric acid. ao(s) + 2Hl(aq) al 2 (aq) + H 2 O(l) (1) 54

55 b) n experiment showed that 14.0 g of calcium oxide were made from a sample of bone of mass 50.0 g. alculate the percentage by mass of calcium in the bone. (3 marks) (Relative atomic masses: O = 16.0, a = 40.1) mass of ao Number of moles of ao made from the sample = molar mass of ao = 14.0 g 56.1 g mol = mol 1 (1) number of moles of a made from the sample = mol Mass of a made from the sample = number of moles of a x molar mass of a = mol x 40.1 g mol 1 = 10.0 g (1) 10.0 g Percentage by mass of a in the sample = 50.0 g x 100% = 20.0% (1) c) Strontium compounds are incorporated into bones because their chemistry is similar to that of calcium compounds. Explain, in terms of electronic structures of the atoms, why calcium and strontium (and their compounds) have similar chemical properties. toms of calcium and strontium have the same number of outermost shell electrons. (1) d) alcium reacts with cold water to give a colourless gas. In a practical lesson, a student added a few calcium granules into a beaker of cold water. Part i) raw a labelled diagram to show how the student could collect the gas produced. (2 marks) (1 mark for correct set-up; 1 mark for correct labels; 0 mark if the set-up is not workable) (2) ii) Write a chemical equation for the reaction. a(s) + 2H 2 O(l) a(oh) 2 (s) + H 2 (g) (1) iii) The student found that evolution of the colourless gas was at first slow but became faster after some time. Suggest an explanation for the student s observation. (2 marks) alcium is covered by a layer of calcium oxide. (1) Reaction between calcium and water starts only when the oxide layer dissolves. (1) 55

56 94 The following set-up was used to determine the empirical formula of an oxide of cobalt (o). The experimental results were as follows: (1) Mass of crucible + lid = g (2) Mass of crucible + lid + cobalt = g (3) Mass of crucible + lid + oxide of cobalt = g a) Give ONE reason why the crucible should be covered with the lid during heating, as shown in the diagram. To prevent the loss of the oxide formed. (1) b) alculate the empirical formula of the oxide of cobalt. (3 marks) Part (Relative atomic masses: O = 16.0, o = 58.9) Mass of cobalt heated = ( ) g = 2.64 g Mass of oxygen in the oxide = ( ) g = 0.96 g Number of moles of atoms that combine Mole ratio of atoms Simplest whole number ratio of atoms obalt Oxygen 2.64 g 58.9 g mol = mol 0.96 g g mol = mol 1 (1) mol mol = 1 = mol mol (1) 1 x 3 = x 3 = 4 (1) the empirical formula of the cobalt oxide is o 3 O 4. c) obalt-60 is widely used as a medical and industrial radiation source. omplete the following information for a 60 o atom. Number of protons Number of neutrons 60 o 27 (0.5) 33 (0.5) 56

57 d) obalt has a hydrated chloride with the chemical formula ol 2 nh 2 O. On strong heating, 22.0 g of the chloride produced 9.99 g of water. What is the value of n? (Relative atomic masses: H = 1.0, O = 16.0, l = 35.5, o = 58.9) (2 marks) Formula mass of ol 2 nh 2 O = x n(2 x ) = n 1 mole of ol 2 nh 2 O contains n moles of H 2 O. i.e. ( n) g of ol 2 nh 2 O contain 18n g of H 2 O g of ol 2 nh 2 O contain 9.99 g of H 2 O. 18n g ( n) g = 9.99 g 22.0 g (1) n = 6 (1) 95 a) oth nitrogen and fluorine are non-metals. raw electron diagrams of the following molecules: i) a nitrogen molecule (1) Part ii) a fluorine molecule b) Nitrogen can react with fluorine to form a compound with a relative molecular mass of The compound contains 42.4% of nitrogen by mass. i) educe the molecular formula of the compound. (3 marks) (Relative atomic masses: N = 14.0, F = 19.0) Suppose there are 100 g of the fluoride, so there are 42.4 g of nitrogen and 57.6 g of fluorine. (1) Number of moles of atoms that combine Mole ratio of atoms Nitrogen Fluorine 42.4 g 14.0 g mol = 3.03 mol 57.6 g g mol = 3.03 mol 1 (1) 3.03 mol 3.03 mol = 1 = mol 3.03 mol (1) 57

58 the empirical formula of the fluoride is NF. Let (NF) n be the molecular formula of the fluoride. Relative molecular mass of the fluoride = n( ) = 66.0 n = 2 (1) the molecular formula of the fluoride is N 2 F 2. ii) raw an electron diagram of the compound, showing electrons in the outermost shells only. (1) 96 The diagram below shows a blast furnace for the production of iron. Part a) i) omplete the table to give information about the main raw materials which are fed into the top of the blast furnace. (3 marks) ommon name Haematite (1) hemical name iron(iii) oxide Limestone calcium carbonate (1) oke (1) carbon ii) Name the raw material which is blasted into the furnace at point. (hot) air (1) iii) Name the substances tapped off at points and. (2 marks) (molten) slag (1) 58 (molten) iron (1)

59 b) t the bottom of the blast furnace, carbon reacts to form carbon dioxide. Write a chemical equation for this reaction. (s) + O 2 (g) O 2 (g) (1) c) The carbon dioxide reacts with more carbon to form carbon monoxide. i) Write a chemical equation for this reaction. O 2 (g) + (s) 2O(g) (1) ii) What is the importance of carbon monoxide in the extraction process? Reducing agent / removes oxygen from iron(iii) oxide (1) iii) Write a chemical equation to show the part played by carbon monoxide in the extraction process. 3O(g) + Fe 2 O 3 (s) 3O 2 (g) + 2Fe(s) (1) d) alculate the mass of iron that can be produced from 399 g of iron(iii) oxide. (3 marks) (Relative atomic masses: O = 16.0, Fe = 55.8) mass of Fe 2 O 3 Number of moles of Fe 2 O 3 = = molar mass of Fe 2 O g g mol 1 = 2.50 mol (1) ccording to the equation, 1 mole of Fe 2 O 3 produces 2 moles of Fe upon reaction. number of moles of Fe produced = 2 x 2.50 mol = 5.00 mol (1) Mass of Fe produced = number of moles of Fe x molar mass of Fe = 5.00 mol x 55.8 g mol 1 Part = 279 g (1) e) Sand (SiO 2 ) is an impurity in the raw materials. The sand is removed from the blast furnace by reacting it with calcium oxide. Write a chemical equation to show how calcium oxide is formed in the blast furnace. ao 3 (s) ao(s) + O 2 (g) (1) f) Large quantities of limestone for use in the blast furnace are obtained from quarries. Give TWO environmental problems that could be caused by quarrying limestone. (2 marks) ny two of the following: Loss of animal habitat (1) / noise pollution (1) / dust pollution (1) / damage to the landscape (1) / traffic density (1) 59

60 97 a) Upon strong heating, silver oxide undergoes decomposition. In a certain experiment, a student heated the oxide strongly while holding a glowing splint in the boiling tube. i) Suggest what would happen to the glowing splint. The glowing splint relights. (1) ii) Write a chemical equation for the decomposition of silver oxide. 2g 2 O(s) 4g(s) + O 2 (g) (1) Part iii) n impure sample of silver oxide of 11.6 g gave 9.17 g of silver upon strong heating. alculate the percentage by mass of silver oxide in the sample. (3 marks) (Relative atomic masses: O = 16.0, g = 107.9) 9.17 g Number of moles of g produced = = mol g mol 1 (1) ccording to the equation, 2 moles of g 2 O undergo decomposition to produce 4 moles of g. number of moles of g 2 O decomposed = mol = mol 2 Mass of g 2 O decomposed = number of moles of g 2 O x molar mass of g 2 O = mol x g mol 1 = 9.85 g (1) Percentage by mass of g 2 O in the sample = 9.85 g 11.6 g x 100% = 84.9% (1) 60

61 b) n oxide of lead, Pb 3 O 4, can be reduced by passing a steam of hydrogen gas over the heated solid. i) Write a chemical equation for the reaction between the lead oxide Pb 3 O 4 and hydrogen gas. Pb 3 O 4 (s) + 4H 2 (g) 3Pb(s) + 4H 2 O(l) (1) ii) State an expected observation in the reaction. Solids with metallic lustre formed. / rops of colourless liquid appeared. (1) iii) Suggest why it is necessary to burn the excess hydrogen in the set-up. Hydrogen is explosive / flammable. (1) c) Is it possible to deduce from the results of the experiments in (a) and (b) that lead occupies a higher position in the metal reactivity series than silver does? Explain your answer. No. The reactivity of silver and lead can only be compared using the same reaction. (1) 98 Many calcium containing compounds such as limestone (calcium carbonate) and gypsum (hydrated calcium sulphate) occur naturally. a) Plaster of Paris is formed by heating gypsum to just above 100 : Part aso 4 2H 2 O gypsum aso H 2O H 2O plaster of Paris i) alculate the percentage by mass of water in gypsum. (2 marks) (Relative atomic masses: H = 1.0, O = 16.0, S = 32.1, a = 40.1) 2 x 18.0 Percentage by mass of H 2 O in gypsum = x x 18.0 x 100% (1) = 20.9% (1) ii) State ONE use of calcium sulphate. lackboard chalk / white line road marking / plaster board / cement (1) iii) What is meant by the term hydrated? ontains water (of crystallization) (1) 61

62 b) In industry, limestone undergoes thermal decomposition to make quicklime. The diagram below represents a limekiln which is used for this process. i) Write a chemical equation for the thermal decomposition of limestone. ao 3 (s) ao(s) + O 2 (g) (1) ii) Name the main element present in coke. arbon (1) Part iii) Name gas which escapes from the top of the kiln. arbon dioxide (1) iv) sample of limestone of mass 330 g was used to make quicklime. 157 g of quicklime were obtained. alculate the percentage by mass of calcium carbonate in the sample. (3 marks) (Relative atomic masses: = 12.0, O = 16.0, a = 40.1) mass of ao Number of moles of ao = molar mass of ao = 157 g = 2.80 mol 56.1 g mol 1 (1) ccording to the equation, 1 mole of ao 3 gives 1 mole of ao upon decomposition. number of moles of ao 3 decomposed = 2.80 mol Mass of ao 3 decomposed = number of moles of ao 3 x molar mass of ao 3 = 2.80 mol x g mol 1 = 280 g (1) Percentage by mass of ao 3 in the sample = 280 g 330 g x 100% = 84.8% (1) v) State ONE use of quicklime. 62 Used in making steel from iron / to neutralize acidity in soil / as a drying agent in industry (1)

63 c) alcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride solution. i) Write a chemical equation for this reaction. ao 3 (s) + 2Hl(aq) al 2 (aq) + O 2 (g) + H 2 O(l) (1) ii) State TWO observations you expect during this reaction. (2 marks) ny two of the following: Effervescence / gas bubbles are given off. (1) / alcium carbonate dissolves. (1) / Heat is evolved. (1) iii) flame test is carried out using calcium chloride. State the flame colour observed. rick-red (1) 99 The following experiment was conducted to determine the percentage by mass of lead(ii) oxide in a sample. Stage 1 Weigh the solid sample. dd excess dilute nitric acid to the sample. Stage 2 Filter the mixture obtained in Stage 1 to remove any undissolved solid. Stage 3 dd excess sodium chloride solution to the filtrate to precipitate out lead(ii) chloride. Stage 4 ollect the lead(ii) chloride precipitate and wash it with distilled water. Stage 5 llow the lead(ii) chloride to dry and weigh it. The results obtained in the experiment are listed below: Mass of the lead(ii) oxide sample = 9.80 g Mass of the lead(ii) chloride obtained = 9.37 g a) The reaction that occurred in Stage 1 can be represented by the following word equation: Part lead(ii) oxide + dilute nitric acid lead(ii) nitrate solution + water Transcribe the word equation into a chemical equation. PbO(s) + 2HNO 3 (aq) Pb(NO 3 ) 2 (aq) + H 2 O(l) (1) b) raw a labelled diagram of the experimental set-up for the filtration in Stage 2. (3 marks) (1 mark for correct set-up; 1 mark for labelling filter funnel and filter paper; 1 mark for labelling residue and filtrate; 0 mark if the set-up is not workable) (3) 63

64 c) The reaction that occurred in Stage 3 can be represented by the following word equation: lead(ii) nitrate solution + sodium chloride solution lead(ii) chloride precipitate + sodium nitrate solution i) Transcribe the word equation into a chemical equation. Pb(NO 3 ) 2 (aq) + 2Nal(aq) Pbl 2 (s) + 2NaNO 3 (aq) (1) ii) Why was excess sodium chloride solution added? To precipitate all the lead(ii) ions as lead(ii) chloride. (1) d) Explain why the precipitate is washed with distilled water in Stage 4. To remove water soluble impurities that adhere to the surface of the precipitate. (1) e) alculate the percentage by mass of lead(ii) oxide in the sample. (3 marks) (Relative atomic masses: O = 16.0, l = 35.5, Pb = 207.2) For the overall reaction: PbO(s) Pbl 2 (s) (not balanced) Part? g 9.37 g mass of Pbl Number of moles of Pbl 2 formed = 2 molar mass of Pbl g = g mol 1 = mol (1) 1 mole of PbO produces 1 mole of Pbl 2. number of moles of PbO present = mol Mass of PbO present = number of moles of PbO x molar mass of PbO = mol x g mol 1 = 7.52 g (1) Percentage by mass of PbO in the sample = 7.52 g 9.80 g x 100% = 76.7% (1) f) State ONE assumption in the calculation. The sample does not contain other ions which form insoluble chloride. (1) 64

65 100 a) alcite is a very pure form of calcium carbonate which reacts with dilute hydrochloric acid according to the following equation: ao 3 (x) + 2Hl(aq) al 2 (y) + H 2 O(z) + O 2 (g) 2.60 g of calcite were added to mole of hydrochloric acid in a beaker. alcite was in excess. i) Give the state symbols represented by x, y and z in the equation. x : s, y : aq, z : l. (1) ii) alculate the mass of calcite left unreacted. (Relative atomic masses: H = 1.0, = 12.0, a = 40.1) mass of ao Number of moles of calcite added = g = = mol molar mass of ao g mol 1 (3 marks) (1) ccording to the equation, 1 mole of ao 3 reacts with 2 moles of Hl mole of Hl reacts with mole of ao 3. Number of moles of calcite left = ( ) mol = mol (1) Mass of calcite left = number of moles of ao 3 x molar mass of ao 3 = mol x g mol 1 = 1.85 g (1) Part iii) escribe how you could check the result obtained in (ii). Separate calcite from the reaction mixture, dry and weigh it. (1) b) n experiment was carried out to determine the percentage by mass of calcium carbonate in a sample of mass 3.10 g. The set-up shown below was used: 65

66 The graph shows the results obtained in the experiment. i) Find, from the graph, the mass of gas liberated from the reaction of the sample with excess hydrochloric acid g (187.6 g g) (1) ii) alculate the percentage by mass of calcium carbonate in the sample. (3 marks) Part (Relative atomic masses: = 12.0, O = 16.0, a = 40.1) mass of O Number of moles of O 2 liberated = g = = mol molar mass of O g mol 1 (1) ccording to the equation for the reaction between ao 3 and Hl, 1 mole of ao 3 produces 1 mole of O 2. number of moles of ao 3 in the sample = mol Mass of ao 3 in the sample = number of moles of ao 3 x molar mass of ao 3 = mol x g mol 1 = 2.50 g (1) Percentage by mass of ao 3 in the sample = 2.50 g 3.10 g x 100% = 80.6% (1) iii) Suggest ONE source of error in the experiment. Some carbon dioxide dissolve in the acid. (1) 66

67 101 Solid magnesium nitride reacts with water according to the following word equation. magnesium nitride + water ammonia + magnesium oxide sample of magnesium nitride of 7.64 g is allowed to react with 15.4 g of water. a) Transcribe the word equation into a chemical equation. Mg 3 N 2 (s) + 3H 2 O(l) 2NH 3 (g) + 3MgO(s) (1) b) ecide which is the limiting reactant. Show how you arrive at your answer. (3 marks) (Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, Mg = 24.3) mass of Mg 3 N g Number of moles of Mg 3 N 2 present = = = mol molar mass of Mg 3 N g mol 1 Number of moles of H 2 O present = mass of H 2 O molar mass of H 2 O = 15.4 g = mol 18.0 g mol 1 (1) (1) ccording to the equation, 1 mole of Mg 3 N 2 reacts with 3 moles of H 2 O to produce 3 moles of MgO. uring the reaction, mole of Mg 3 N 2 reacts with mole of H 2 O. Therefore Mg 3 N 2 is the limiting reactant. It limits the amount of MgO obtained. (1) c) alculate the mass of magnesium oxide obtained. Mass of MgO obtained = number of moles of MgO x molar mass of MgO = mol x 40.3 g mol 1 Part = 9.15 g (1) 102 student tried to extract lead from lead(ii) oxide. He placed 10.0 g of lead(ii) oxide and 10.0 g of carbon powder in a crucible and heated the mixture with a unsen flame. a) raw an experimental set-up for the extraction of lead(ii) oxide. (2 marks) (1 mark for correct set-up; 1 mark for correct labels; 0 mark if the set-up is not workable) (2) 67

68 b) i) Write a chemical equation for the reaction involved. 2PbO(s) + (s) 2Pb(s) + O 2 (g) (1) ii) Suggest ONE observation of the experiment. Solids with metallic lustre would be observed. (1) c) i) etermine which reagent is in excess. (3 marks) (Relative atomic masses: = 12.0, O = 16.0, Pb = 207.2) mass of PbO Number of moles of PbO = molar mass of PbO = 10.0 g g mol = mol 1 (1) mass of Number of moles of = molar mass of = 10.0 g = mol 12.0 g mol 1 (1) ccording to the equation, 2 moles of PbO react with 1 mole of. Hence mole of PbO would react with mole of. Therefore carbon is in excess. (1) ii) alculate the maximum mass of lead that could be obtained. Maximum mass of Pb obtained = number of moles of Pb x molar mass of Pb = mol x g mol 1 Part = 9.28 g (1) d) In fact, the student only obtained 7.10 g of lead. i) alculate the percentage yield of lead. Percentage yield of lead = 7.10 g 9.28 g x 100% = 76.5% (1) ii) Suggest ONE reason why the student cannot get the maximum mass of lead. The temperature is not high enough. / Not enough time allowed for the reaction to take place. (1) e) nother oxide of lead has a chemical formula Pb 3 O 4. Pb 3 O 4 is known to be a mixed oxide composed of PbO and PbO 2. educe the mole ratio of PbO to PbO 2 in Pb 3 O 4. (2 marks) Let the mole ratio of PbO : PbO 2 be x : y. Number of moles of Pb Number of moles of O = x + y x + 2y = 3 4 (1) Pb 3 O 4 is a mixture of PbO and PbO 2 in a mole ratio of 2 : 1. x = 2, y = 1 (1) 68

69 103 mmonia can be manufactured from nitrogen and hydrogen according to the following reaction: N 2 (g) + 3H 2 (g) 2NH 3 (g) a) What information can be obtained from the double arrow in the equation? The reaction is reversible. (1) b) alculate the theoretical yield of ammonia produced from 72.8 g of nitrogen and excess hydrogen. (Relative atomic masses: H = 1.0, N = 14.0) mass of N Number of moles of N 2 = g = = 2.60 mol molar mass of N g mol 1 (2 marks) (1) ccording to the equation, 1 mole of N 2 produces 2 moles of NH 3. number of moles of NH 3 produced = 2 x 2.60 mol = 5.20 mol Theoretical yield of NH 3 = number of moles of NH 3 x molar mass of NH 3 = 5.20 mol x 17.0 g mol 1 = 88.4 g (1) c) The percentage yield of ammonia is 15.0%. What is the mass of ammonia produced? Mass of NH 3 produced = 88.4 g x 15.0% = 13.3 g (1) d) mmonia reacts with copper(ii) oxide according to the following word equation: ammonia + copper(ii) oxide nitrogen + water + copper Part i) Transcribe the word equation into a chemical equation. 2NH 3 (g) + 3uO(s) N 2 (g) + 3H 2 O(l) + 3u(s) (1) ii) In an experiment, 20.4 g of ammonia were allowed to react with 159 g of copper(ii) oxide. alculate the mass of nitrogen obtained. (4 marks) (Relative atomic masses: H = 1.0, N = 14.0, O = 16.0, u = 63.5) Number of moles of NH 3 = mass of NH g = molar mass of NH g mol 1 = 1.20 mol Number of moles of uo = mass of uo molar mass of uo = 159 g 79.5 g mol 1 = 2.00 mol (1) (1) ccording to the equation, 2 moles of NH 3 react with 3 moles of uo. uring the reaction, 1.20 moles of NH 3 react with 1.8 moles of uo. Therefore NH 3 is the limiting reactant. It limits the amount of N 2 obtained. (1) number of moles of N 2 obtained = 1.20 mol = mol 2 Mass of N 2 obtained = number of moles of N 2 x molar mass of N 2 = mol x 28.0 g mol 1 = 16.8 g (1) 69

70 104 a) The set-up below was used to investigate the rusting of iron. i) In which tube(s) will rusting NOT occur? Explain your answer. (3 marks) Rusting will not occur in tubes and. (1) In tube, the zinc strip provides sacrificial protection. (1) In tube, there is no oxygen. (1) ii) In which tube will the rusting be the most serious? Explain your answer. (2 marks) Tube. (1) The very dilute hydrochloric acid speeds up the rusting process. (1) b) The Statue of Liberty is made from copper attached to an iron frame. Part Statue of Liberty i) Why does the iron frame rust more quickly when attached to the copper? opper is less reactive than iron. Iron corrodes instead of copper. (1) ii) The statue sits on an island surrounded by sea water. Why does the sea water increase the rate of rusting? Sea water contains sodium chloride. (1) iii) Explain why green patches appear on the statue. opper(ii) ions are formed when the copper corrodes. (1) 70

71 105 Four iron rods are placed separately in gel with a rust indicator containing potassium hexacyanoferrate(iii), and allowed to stand in air for some time. omplete the following table by writing down the observation and giving the relevant explanation for each case. (8 marks) ase Observation Explanation a) Iron rod fully plated with zinc No observable change (1) The iron rod does not rust as the zinc coating prevents oxygen and water from reaching the iron. (1) b) Iron rod fully plated with tin No observable change (1) The iron rod does not rust as the tin coating prevents oxygen and water from reaching the iron. (1) c) Iron rod partly plated with zinc No observable change (1) The iron rod does not rust as zinc provides sacrificial protection. (1) Part d) Iron rod partly plated with tin blue colour appears (1) The iron rod rusts rapidly as iron is in contact with tin, a less reactive metal. (1) 71

72 106 The table gives information about some metals. Name of the metal ost of one tonne of the metal in September 2007 (HK$) Percentage by mass of the metal in the Earth s crust (%) luminium Platinum Iron Gold a) Use information in the table to suggest why gold and platinum are very expensive metals. Very small percentage of both metals exists in the Earth s crust. (1) b) Explain why gold ornaments are usually made from an alloy of gold and copper rather than pure gold. The alloy is stronger than pure gold. (1) c) Iron was discovered about four thousand years ago while aluminium was discovered about two hundred years ago. Suggest a relationship between the reactivity and the year of discovery of metals. Less reactive metals were discovered first and more reactive metals were discovered later. (1) Part d) luminium is extracted by the electrolysis of molten aluminium ore. i) How is iron extracted from iron ore in a blast furnace? (2 marks) uring the extraction, a mixture of iron ore, coke and limestone is added at the top of the blast furnace. (1) arbon monoxide is produced in the process. The carbon monoxide reduces the iron ore to produce iron. (1) ii) Suggest why aluminium is more expensive than iron. large amount of electricity is needed for the extraction of aluminium. This makes aluminium expensive. (1) e) oth aluminium and iron can be used to make window frames. i) Suggest how each metal is treated to prevent corrosion in this application. (2 marks) The aluminium undergoes anodization to increase the thickness of the oxide layer. This makes the aluminium much more resistant to corrosion. (1) The iron is painted so as to prevent oxygen and water from reaching it. The paint layer protects the iron beneath from rusting. (1) 72

73 ii) Explain why most window frames are now made of aluminium instead of iron. (2 marks) s soon as the paint on the iron is scratched, rusting starts. (1) luminium reacts with oxygen in the air to give an even coating of oxide on the surface. The oxide layer is not permeable to oxygen and water. It protects the metal beneath from further attack. (1) f) The diagram below shows a can of fruit juice. The body of the can is made of iron coated with tin. The top of the can and the ring-pull are made of aluminium. made of aluminium made of iron coated with tin i) Suggest ONE reason why the iron body is coated with tin. Part To protect iron from rusting. (1) ii) Suggest ONE reason why aluminium, rather than iron, is used for making the ring-pull. luminium is softer than iron so that the ring-pull can be pulled off more easily. (1) iii) There is a trend for manufacturers to use aluminium cans for fruit juice. Suggest ONE advantage and ONE disadvantage of this action. (2 marks) dvantage: luminium is lighter than iron. / luminium can be recycled more easily. / luminium is more corrosion resistant than iron. / luminium can be dyed more easily. (1) isadvantage: luminium is more expensive than iron. / luminium is not as strong as iron. (1) 73

74 107 Read the passage below and answer the questions that follow. luminium luminium is all around us. It is light and strong, corrosion resistant, durable, and highly conductive. common ore of aluminium is bauxite. luminium is extracted from this ore by a chemical process that uses a large quantity of energy. To produce aluminium from recycling uses just 5% of the energy needed for extraction of the metal from its ores. Recycling 1 kilogram of aluminium saves about 4 kilograms of aluminium ore; 4 kilograms of raw materials used in extracting the metal from its ores; and 14 kilowatt-hours of electricity. To make metal recycling worthwhile, there must be a steady supply of metal waste and the necessary technology to separate the required metal from waste materials. a) Suggest the main metallic compound in bauxite. luminium oxide (1) b) Name the chemical process for obtaining aluminium from bauxite. Part Electrolysis (1) c) Suggest TWO benefits of recycling metals. (2 marks) ny two of the following: Metal resources can be saved. (1) / Fuel can be saved. (1) / Environmental impact due to metal waste and mining can be reduced. (1) / Public awareness of conservation can be raised. (1) d) Suggest TWO problems associated with recycling. (2 marks) ny two of the following: The cost is high. (1) / It is difficult to get people to save metal waste. (1) / It is difficult to sort the metal waste. (1) 74

75 e) Explain why iron was discovered about four thousand years ago while aluminium was discovered about two hundred years. (2 marks) luminium is more reactive than iron. (1) The extraction of iron is easier than that of aluminium. (1) f) Suggest ONE use of aluminium. Making aeroplanes / window frames / overhead power cables / foils (1) g) One of the special properties of aluminium is that it has a high corrosion resistance. i) Explain why aluminium has such a high corrosion resistance. There is a layer of aluminium oxide attached to the metal surface. (1) ii) The corrosion resistance of aluminium can be enhanced by a method. (1) Name this method. luminium anodization (1) (2) raw a labelled diagram of the laboratory set-up used for this method. (2 marks) Part (1 mark for correct set-up; 1 mark for correct labels; 0 mark if the set-up is not workable) (2) 75

76 108 Read the passage below and answer the questions that follow. Magnesium lthough magnesium is the sixth most abundant element in the Earth s crust, it is never found free in nature. Scientists adopt different methods to extract magnesium from magnesium oxide. In 1828, a scientist obtained magnesium by two steps. In the first step, magnesium oxide was allowed to react with chlorine and carbon to form magnesium chloride. In the second step, the magnesium chloride reacted with potassium to give magnesium. In 1951, some scientists adopted another chemical process to obtain magnesium from magnesium chloride. Potassium is not used in this process, and there is even no need to use any other chemicals. Today, magnesium is most often obtained from sea water. The extraction of magnesium from sea water involves three steps. In the first step, slaked lime is added to sea water to precipitate the magnesium ions as magnesium hydroxide. In the second step, the magnesium hydroxide is heated in a steam of hydrogen chloride gas to give magnesium chloride. In the final step, magnesium is extracted from the magnesium chloride. a) Name the most abundant metal in the Earth s crust. luminium (1) b) onsider the extraction method used in Part i) The reaction that occurred in the first step can be represented by the following word equation: magnesium oxide + chlorine + carbon magnesium chloride + carbon dioxide Transcribe the word equation into a chemical equation. 2MgO(s) + 2l 2 (g) + (s) 2Mgl 2 (s) + O 2 (g) (1) ii) Name the type of reaction between potassium and magnesium chloride. Why can potassium react with magnesium chloride to give magnesium? (2 marks) isplacement reaction (1) Potassium is more reactive than magnesium. (1) iii) raw an electron diagram of magnesium chloride, showing electrons in the outermost shells only. (1) 76