Year 10 Chemistry GJ Zahra B.Ed (Hons). St Albert the Great College

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1 Periodicity Year 10 Chemistry GJ Zahra B.Ed (Hons). St Albert the Great College Chapter 10 Name & Surname Class Mark the following statements True (T), False (F) or Unsure (U) Across a period there is a change from metallic to non-metallic character Reactivity of elements always increases down a periodic group Atomic size increases down a group If X is in group 3 and Y is in group 1, when they react they form Y 3 X Before Lessons After Lessons Aluminium is a metal and thus forms a basic oxide, Al 2 O 3 All metals are hard and have high densities Alkali metals form basic oxides and alkaline aqueous hydroxides Copper reacts with nitric acid to give copper (II) nitrate Transition metals have variable valencies and form coloured compounds The formula of Iron (III) sulfide is FeS 3 The reaction between iron and chlorine or with hydrogen chloride gives Iron (III) chloride Iron (II) hydroxide gets easily oxidized Copper compounds are usually more stable than iron compounds An alloy is a mixture of metals or of metals with non-metals Noble gases exist as free atoms at rtp The reaction of halogens with iron produces iron (III) halides All metals are solid at stp All halogens exist as diatomic molecules

No one believed Mendeleev at first and the periodic table only gained solid ground when Gallium was discovered in 1975. The first version of the periodic table.

2 Periodicity Page 2 Dmitri Ivanovich Mendeleev was a Russian chemist and inventor. He was the first to classify elements in a crude version of the periodic table and used this classification to predict properties of elements yet to be discovered in No one believed Mendeleev at first and the periodic table only gained solid ground when Gallium was discovered in The first version of the periodic table. Periodicity The periodic table has all the elements arranged in groups (columns) and periods (rows). Elements show similarities with other elements in the same group (which have the same number of valence electrons), and with other elements in the same period (which have the same number of electron shells). Periodicity is the study of trends in the periodic table. Along a Period: The number of protons increases while electrons are added to the same shell. As a result, there is more attraction between the outer shell and the nucleus. Atomic size decreases along a period. Electrons are harder to lose. Thus, there is a change from metallic to non-metallic character, with metalloids lying usually in between Oxides change from basic to acidic, with amphoteric oxides lying usually in between Electrons are harder to lose. Thus metals become less reactive along a period. Due to higher nuclear charge, electrons are more easily gained. Thus non-metals become more reactive along a period (excluding the noble gases). Metal atoms are more bound in a metallic structure, due to more electrons being lost and a higher charge of cations. As a result, hardness, density and melting points of metals increase along a metallic period. Down a Group: The number of protons increases while electrons are added to new shells. As a result, atomic size increases down a group. Electrons are easier to lose since they are farther from the nucleus. Thus, there is an increase in metallic character down a group. Electrons are easier to lose. Thus metals become more reactive down a group. Due to increased distance from the nucleus, electrons are harder to gain. Thus non-metals become less reactive down a group. Metals atoms are less bound in a metallic structure due to lower attracted towards electrons. As a result, hardness, density and melting points decrease down a metallic group.

4 GJ Zahra B.Ed (Hons). St Albert the Great College Elements in the Periodic Table From the first thirty elements of the periodic table (H to Zn) choose an element that: Page 4 1 Is a halogen in period 3 2 Is an alkali metal in period 3 3 Is an alkaline earth metal in period 3 4 Burns with a squeky pop 5 Has the electronic configuration 2,8,6 6 Gives an amphoteric oxide 7 Can give a neutral oxide 8 Is the most reactive metal 9 Is the most reactive non-metal Exercise Has the smallest atom 11 Has the largest atom 12 Relights a glowing splint 13 Is purified by electrolysis 14 Is a yellow green gas 15 Has a variable valence with 2 being the most stable 16 The least reactive element 17 Exists as a diatomic molecule 18 Is a monoatomic gas that makes up 0.9% of air 19 When placed in cold water sinks and effervescence is observed 20 Reacts slowly with cold water but reacts violently with steam

Periodicity Page 5 Group 1: The Alkali Metals Group 1 metals are called the alkali metals because they produce strongly alkaline solutions when reacting with water.

They are soft, silvery, highly reactive metals with low melting points and densities. They quickly tarnish on exposure to air due to their fast reactions with oxygen.

The difference in reactivity between sodium and potassium can be shown by their reaction with water: potassium reacts more vigorously.

5 Periodicity Page 5 Group 1: The Alkali Metals Group 1 metals are called the alkali metals because they produce strongly alkaline solutions when reacting with water. Group 2 metals are called the alkaline earth metals because they tend to give weakly alkaline solutions when they react with water and because they are major components of the Earth s crust. They are soft, silvery, highly reactive metals with low melting points and densities. They quickly tarnish on exposure to air due to their fast reactions with oxygen. As a result, they are stored under oil. Reactivity increases down the group as the elements get larger and electrons are less attracted by the nucleus and thus easier to lose. The difference in reactivity between sodium and potassium can be shown by their reaction with water: potassium reacts more vigorously. Compounds containing group 1 metals are usually very stable and thus the metals are extracted from their ores by electrolysis. The alkali metals are very reactive and react vigorously with oxygen, cold water and with non-metals. It is not usually possible to carry displacement reactions using alkali earth metals, since their reaction with water will happen instead. Group 2: The Alkaline Earth Metals Group 2 metals are fairly reactive. They are less reactive than group 1 metals because they have more electrons to lose and also because these electrons are more strongly attracted towards the nucleus (it has more protons). Melting points and hardness are higher than those of group 1 metals. Group 2 metal compounds are also quite stable, and alkaline earth metals are also usually obtained by electrolysis. Alkaline earth metals react with oxygen, slowly with cold water, but more vigorously with steam, and with a variety of non-metals. The reaction of group 2 metals with an acid can be safely carried out. Magnesium can also be used for displacement reactions. Calcium is widely found as limestone, which is mainly calcium carbonate. It can be heated to obtain quick lime (CaO), which can be reacted with water to obtain slaked lime (Ca(OH)2). Limestone is also used for construction, while slaked lime is used for acid soil treatment and to increase the rate of hardening of plaster. Exercise 10.2 Write balanced chemical equations for the reaction between: Limestone is mainly formed calcium carbonate. 1. Sodium and oxygen 2. Potassium and water 3. Lithium and chlorine 4. Magnesium and oxygen 5. Calcium and water 6. Magnesium and steam 7. Formation of slaked lime starting from calcium carbonate

6 Chapter 10 Page 6 Name: Periodic Trends Exercise 10.3 GJ Zahra B.Ed (Hons). St Albert the Great College Ex A: What happens (increase, decrease or remain the same) to the following properties 1. Down a typical metallic group 2. Across a typical metallic period Property 1. Down a metal group 2. Across a metal period Number of protons Number of electrons Number of electron shells Distance of outermost electron from nucleus Atomic Size Number of valence electrons Stability ( strength ) of metallic structure Reactivity Hardness Stability of compounds Ex B: Give the name or symbol of an element that Burns with a bright white flame Its main ore is Bauxite Is in period 2 and exists as a monoatomic gas at rtp Is a soft metal in period 4 that can be cut with a knife Reacts violently with steam but very slowly with cold water When placed in water, produces an alkaline solution and a lilac flame Exists as an unreactive, diatomic gas Has a variable oxidation number, with 3 being the most stable one Is purified by electrolysis A main group (not transition) element with an amphoteric oxide

Periodicity Page 7 Transition metals typically form coloured compounds. Haematite, the main ore from which iron is obtained. A painting of an old German blast furnace.

They are hard, dense solids with high melting points. Like other metals, they are also good conductors of electricity, malleable and ductile.

They are widely used as catalysts, for example: Manganese (IV) oxide in the decomposition of hydrogen peroxide An iron based catalyst in the production of ammonia Vanadium (V) oxide in the oxidation

An alloy is a mixture of metals (eg brass is made from copper and zinc), or of metals with nonmetals (eg steel is made from iron and carbon). Iron is a transition metal that is very much in use.

7 Periodicity Page 7 Transition metals typically form coloured compounds. Haematite, the main ore from which iron is obtained. A painting of an old German blast furnace. Blast furnaces first existed in China in the 5th century BC. The Transition Metals Iron The transition metals are very different from main-group metals. They are hard, dense solids with high melting points. Like other metals, they are also good conductors of electricity, malleable and ductile. The chemistry of transition metals is also different than that of other metals. They are typically unreactive, form coloured compounds and have variable valencies. They are widely used as catalysts, for example: Manganese (IV) oxide in the decomposition of hydrogen peroxide An iron based catalyst in the production of ammonia Vanadium (V) oxide in the oxidation of SO2 to SO3 in the production of sulfuric acid). Transition metals are also widely used as alloys. An alloy is a mixture of metals (eg brass is made from copper and zinc), or of metals with nonmetals (eg steel is made from iron and carbon). Iron is a transition metal that is very much in use. It is used for construction, cars, catalysis and to make numerous alloys such as steel. Iron is found naturally as Fe2O3 in an ore called haematite and is reduced to iron using carbon monoxide in a process called the blast furnace. The steps are as follows: Haematite is mixed with limestone (calcium carbonate) and coke (carbon) and in the blast furnace where several reactions take place. Coke reacts with oxygen to form carbon dioxide. C(s) + O2(g) CO2(g) The limestone decomposes to give calcium oxide and more carbon dioxide. CaCO3(s) CO2(g) + CaO(s) Carbon dioxide reacts with coke to give carbon monoxide. C(s) + CO2(g) 2 CO(g) Carbon monoxide reacts with iron (III) oxide and reduces this to iron. A modern blast furnace. These are usually at least 30 metres high, made of steel lined with fireproof bricks. Fe2O3(s) + 3 CO(g) 3 CO2(g) + 2 Fe(s)

Chapter 10 Page 8 The main impurity in haematite is silica, SiO2. Calcium oxide formed in the second step reacts with silica to form slag, which floats on the liquid iron.

8 Chapter 10 Page 8 The main impurity in haematite is silica, SiO2. Calcium oxide formed in the second step reacts with silica to form slag, which floats on the liquid iron. SiO2(s) + CaO(s) CaSiO3(l) When the slag solidifies, it is sold and used mainly for road building. Only some of the iron is left to solidify, the rest is taken while still hot to make steel. Cast iron is hard, but brittle. It is used for railways and storage tanks amongst other things. Steel exists as a variety of alloys each having different percentages of components. For example, stainless steel used for cutlery and watches is different than flat carbon steel used to make appliances and bodies of cars, trains and ships. Properties of Iron Iron reacts with water and oxygen to form rust (hydrated iron (III) oxide): 4 Fe(s) + 2 H2O(l) + 3 O2(g) 2 Fe2O3 H2O (s) Iron also reacts with steam to form black iron (II) oxide and hydrogen gas: Fe(s) + H2O(g) FeO(s) + H2(g) When iron is heated, it reacts vigorously with chlorine. The resultant chloride is iron (III) chloride, because chlorine is a strong oxidizing agent. 2 Fe(s) + 3 Cl2(g) 2 FeCl3(s) Iron (II) chloride can be prepared by the reaction of iron with hydrochloric acid, since HCl is nonoxidizing. FeCl2 is easily oxidized to iron (III) by aerial oxidation or by passing chlorine gas through the solution. Fe(s) + 2 HCl(aq) FeCl2(aq) + H2(g) Iron (II) hydroxide can be prepared by the reaction between iron (II) ions (for example in Iron (II) sulfate) and hydroxide ions (in for example sodium hydroxide). FeSO4(aq) + 2 NaOH(aq) Na2SO4(aq) + Fe(OH)2(s) Although Iron(II) hydroxide is a mud green solid, it is quickly oxidized to assume a rusty colouration. Iron (III) hydroxide can be prepared by the reaction between iron (III) ions, for example in iron (III) chloride, and hydroxide ions, for example in sodium hydroxide. The resultant brown-red precipitate is iron (III) hydroxide. This reaction is used as the test for iron (III) cations. FeCl 3(aq) + 3 NaOH (aq) 3 NaCl (aq) + Fe(OH) 3(s)

9 Exercise 10.4 Page 9 GJ Zahra B.Ed (Hons). St Albert the Great College Iron & The Blast Furnace Answer the following questions 1. Iron is an example of a transition element. Give three physical and three chemical properties of transition elements. 2. Name the main ore of iron 3. What three solids are introduced in the blast furnace? 4. The main reaction for the blast furnace is that between iron(iii) oxide and carbon monoxide. Write down a balanced chemical equation for this reaction. 5. Write two ionic half equations for the equation in (4). Clearly label each half equation as oxidation or reduction. 6. Explain, including relevant chemical equations, how carbon monoxide is obtained in the blast furnace. 7. What is the role of carbon monoxide in the blast furnace? Explain. 8. What is the main impurity in the ore of iron and how is this removed? 9. Write equations for the reactions between iron and: a. Water b. Oxygen and water c. Chlorine d. Hydrogen chloride 10.Explain how pure iron (II) hydroxide can be prepared in the lab starting from iron and any other chemicals of your choice. Your answer must include: a. Experimental details of the compounds used and their quantities (excess or limiting) b. Balanced chemical equations for the reactions taking place c. Well labelled diagrams of any adopted separation techniques d. How the iron (II) hydroxide can be stored to avoid oxidation to iron (III) hydroxide 11.A modern day blast furnace can produce up to 80,000 tonnes of iron per week. a. What is the percentage of iron in iron (III) oxide? b. Calculate the mass of iron(iii) oxide needed to produce 80,000 tonnes of iron assuming 100% efficiency and that haematite consists solely of iron (III) oxide. c. Calculate the mass of carbon monoxide needed for the reaction. 12.The concentration of a solution of iron (III) chloride was found by titration with sodium hydroxide. Given that 25cm 3 of the FeCl3 required 37.5cm 3 of 0.2 mol/dm 3 NaOH, calculate the concentration of the iron (III) chloride solution (Ans: 0.1 mol/dm 3 ).

Chapter 10 Page 10 Copper Copper is used in piping, electrical wiring, coinage, brass instruments, and cookware amongst other applications. Copper is purified by electrolysis.

2 Cu(s) + O2(g) 2 CuO(s) Copper metal does not react with dilute acids.

Rather than being a neutralization reaction, this is a redox reaction.

10 Chapter 10 Page 10 Copper Copper is used in piping, electrical wiring, coinage, brass instruments, and cookware amongst other applications. Copper is purified by electrolysis. Copper does not react with water; however it reacts slowly with oxygen to form black copper (II) oxide. Like in aluminium, this oxidized layer protects copper from further oxidation. 2 Cu(s) + O2(g) 2 CuO(s) Copper metal does not react with dilute acids. However, copper reacts with concentrated sulfuric acid and concentrated nitric acid to produce the respective copper (II) salts together with sulfur dioxide or nitrogen dioxide. Rather than being a neutralization reaction, this is a redox reaction. Cu(s) + 2 H2SO4(l) CuSO4(aq) + SO2(g) + 2 H2O(l) Hydroxides, carbonates and nitrates of copper decompose when heated to give copper (II) oxide, which is heat stable. CuCO3(s) 2 CuO(s) + CO2(g) Copper reacts slowly with oxygen to form black copper (II) oxide. This is formed as a thin layer that prevents the copper underneath from reacting with further oxygen. Cu(OH)2(s) CuO(s) + H2O(g) 2 Cu(NO3)2(s) 2 CuO(s) + 4 NO2(g) + O2(g) Copper(II) oxide is a typical basic oxide and can be reacted with various acids to prepare copper (II) salts. CuO(s) + H2SO4(aq) CuSO4(aq) + H2O(l) As copper is low in the reactivity series, it can be obtained by reduction of its oxide with hydrogen or another reducing agent. CuO(s) + H2(g) Cu(s) + H2O(g) Copper reacts with concentrated nitric acid to produce a green solution of copper (II) nitrate and brown nitrogen dioxide gas. The reaction can be very dangerous due to the heat evolved and the toxicity of nitrogen dioxide. Exercise 10.5 Excess copper is added to concentrated nitric acid and a salt X is obtained together with a brown gas A. The obtained mixture was diluted and filtered. The filtrate is evaporated and the obtained solid is heated strongly to obtain a solid Y and two gases, B and C. Hydrogen is passed over Y and on strong heating a reddish solid Z is obtained. 1. Deduce the identity of X, Y and Z. 2. Write chemical equations for the thermal decomposition of X. 3. Describe tests to identify the gases B and C. 4. How can solid Z be purified in industry? Describe. 5. Calculate the mass of H2 needed to react with g of Y (Ans:5g). Chile is the world s largest producer of copper, with a production exceeding five billion tons of copper per year.

Periodicity Page 11 All of the halogens exist as diatomic molecules. They have different colours and occur in different physical states.

Since non-metals react by gaining electrons, larger atoms are less reactive as the nucleus is less able to attract electrons which lie farther away from it.

The halogens have different colours and exist in different physical states.

11 Periodicity Page 11 All of the halogens exist as diatomic molecules. They have different colours and occur in different physical states. Group 7: The Halogens Down a group, nonmetals also increase in size, however this have a different effect on their reactivity than metals. Since non-metals react by gaining electrons, larger atoms are less reactive as the nucleus is less able to attract electrons which lie farther away from it. Melting and boiling points increase down a group as the RMM of halogen m diatomic molecules increases. All halogens are found as diatomic molecules. The halogens have different colours and exist in different physical states. Chlorine is a yellow-green gas, bromine is a volatile brown liquid, while iodine is a violet/black solid which sublimes on heating. Chlorine reacts with water to give hydrochloric acid and chloric (I) acid. For bromine the reaction occurs at a slower rate. Iodine does not dissolve in or react with water. HOCl is a component in bleach and this is why chlorine bleaches litmus paper after turning it red. Cl2(g) + H2O(l) HOCl(aq) + HCl(aq) Br2(l) + H2O(l) HOBr(aq) + HBr(aq) Like metals, halogens can displace each other depending on their reactivity, where chlorine is the most reactive and iodine the least. 2 NaI(aq) + Br2(l) 2 NaBr(aq) + I2(s) MgBr2(aq) + Cl2(g) MgCl2(aq) + Br2(l) Group 1 and Group 2 metals react with the halogens to form the simple metal halides. The vigour of the reaction decreases on going from chlorine to iodine. I2(s) + 2 Na(s) 2 NaI(s) Iron also reacts with the halogens with decreasing vigour from chlorine to iodine. With chlorine and bromine, Iron forms the Iron(III) halide. Fluorine is a pale yellow gas. It is the most reactive non-metal, extremely dangerous and toxic. Astatine has never been properly viewed, since it decays by radioactivity. There are less than 25g of astatine on Earth. 3 Br2(l) + 2 Fe(s) 2 FeBr3(s) However iodine is less reactive and does not manage to oxidize iron to iron(iii). Instead iron(ii) iodide is formed. This shows that iodine is a weaker oxidizing agent than chlorine and bromine. I2(s) + Fe(s) FeI2(s) Chlorine is used in swimming pools, bleach and to kill bacteria in drinking water. Bromine is used in disinfectants and dyes. Iodine is used to kill germs on the skin without damaging the skin since it is only a weak oxidizing agent.

$Noble gases are obtained from the fractional distillation of liquid air. Their uses include: To fill light bulbs Provide an inert atmosphere even in very high temperatures.$ Advertising signs Lasers Cooling agents Exercise 10.6 1. Explain why the reactivity of metals increases down a group. 2. Explain why the reactivity of non-metals decreases down a group. 3.

Advertising signs Lasers Cooling agents Exercise 10.6 1. Explain why the reactivity of metals increases down a group. 2. Explain why the reactivity of non-metals decreases down a group. 3.

12 Chapter 10 Group 8: The Noble Gases Group 8 elements are known as the Noble gases. They have 8 valence electrons and are thus unreactive and found naturally as monoatomic (free, single atoms). Noble gases are obtained from the fractional distillation of liquid air. Their uses include: To fill light bulbs Provide an inert atmosphere even in very high temperatures. Advertising signs Lasers Cooling agents Exercise Explain why the reactivity of metals increases down a group. 2. Explain why the reactivity of non-metals decreases down a group. 3. Why do halogens exist naturally as diatomic molecules? Draw the bonding in a molecule of chlorine to further illustrate your answer. 4. Why do the noble gases occur naturally as monoatomic particles? 5. Give a balanced chemical reaction for each of the following reactions: a. Sodium with water b. Magnesium with steam 6. Calculate the mass of each of the following substances needed to completely react with 42g of iron. a. Hydrogen chloride b. Chlorine c. Copper with conc. sulfuric acid d. Copper (II) nitrate with zinc c. Bromine d. Iodine Page 12 Group 8 are called the noble or inert gases due to their high unreactivity. Neil Bartlett, aged 30, was the first to predict the formation of a compound of Xenon in One compound has been synthesized from Argon in No experimentally confirmed compounds of helium and neon exist, yet. All noble gas compounds are unstable and only formed under extreme conditions. 7. Fully explain the blast furnace. Use a diagram and chemical equations. 8. When 100g of iron (II) nitrate are heated, a black solid A is obtained along with two gases, B and C. When excess hydrobromic acid, HBr, is added to A, a solution of D is formed. Excess chlorine is bubbled through the solution to obtain a brown, dense liquid D and a greenish solution E, which turns into F, a dark yellow solution. a. Write chemical equations for all chemical changes taking place. b. Deduce the identity of substances A, B, C, D, E and F. c. Describe a chemical test to confirm the identity of E and F. d. Assuming reactions to be 100% efficient, calculate the mass of D obtained. The noble gases glow brightly when an electric discharge is passed through them, and so are used as advertising signs: neon tubes glow red, xenon blue, and krypton bluish-white; argon tubes glow pale red at low pressures, blue at high pressures.

Our country, our future S2 CHEMISTRY DURATION: 2 HOUR

Our country, our future S2 CHEMISTRY Exam 1 DURATION: 2 HOUR INSTRUCTIONS: This paper consists of two sections A and B, Attempt all questions in section A and B For section A, circle the most correct alternative