Cozo College. BOYS' Secondary victoria Cozo, Malta 'Ninu Cremona' Half Yearly Examination ANSWER ALL QUESTIONS

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1 Cozo College BOYS' Secondary victoria Cozo, Malta 'Ninu Cremona' ooo Half Yearly Examination Form 4 J.L. Chemistry Time: 1'/z Hours Name: Class: Useful Data: Q=It Faraday Constant = C SECTION A ANSWER ALL QUESTIONS Question 1: Elements in' the same Group of the_periodic Table show a similarity in physical and chemical properties. The' elements also show a trend in reactivity. Lithium is in Group 1 of the Periodic Table. Use your knowledge of the Group 1 metals (e.g. Na, K) to answer the following questions about Lithium. (a) (i) What is the number of electrons in the outer shell of a lithium atom? (1) (ii) Write down the formula for the lithium ion. (1) (b) Predict one physical property that you would expect lithium to show. (1) (c) How would you expect lithium to be extracted from its compounds? (,1)

2 (d) (i) State one thing you would expect to see when lithium is added to dilute hydrochloric acid. (1) (ii) Give a balanced equation for the reaction of lithium: with water with dilute hydrochloric acid. (4) (e) Would you expect lithium to be more, or less reactive, than sodium and potassium? (I) Question 2: a) Aluminium powder reacts, on heating, with iron (III) oxide to liberate the metal iron according to the equation: 2Al + Fe203-- Ah03+ 2Fe i) What conclusion can be drawn about the relative degree of reactivity of the two metals aluminium and iron? (1) ii) Give a reason why aluminium is not used to extract iron from iron (III) oxide in this way (1) iii) Give the name of one other metal which you would expect to be released from its oxide by heating with aluminium powder. (I) b) The method and form of energy used to extract a metal from its oxide depends on the stability of the metal oxide, which in turn, is related to the position of the metal in the reactivity series. The uses of metals depend on their properties. Complete the table below: 2

3 type of energy used to bring about the extraction the other substance required for the extraction in addition to the oxide use of the metal Aluminium Iron (6) c) All methods of extracting metals involve the same type of reaction. Name this type of reaction. (1 Question 3: a) The outline diagram below shows different areas ofthe Periodic Table. A B c D E Give the letter of the area in which you would find: i) elements that are umeactive and do not tend to form compounds ii) the most reactive metals iii) a metal which is borderline with non-metals and whose oxide IS amphoteric _ iv) a solid non-metal that burns in air to form an acidic oxide v) a metal that has a variable valency and forms coloured ions vi) a halogen vii) an element that reacts with water to form an alkaline solution b) Give the number of electrons in the outer shell of the atoms of; i) most noble gases 3

4 ii) metals that form ions ofthe type X2+ iii) non-metals that form ions ofthe type X- Question 4: The following chemical equation is an example of a Redox reaction. (10 marks) F2 (g) + 2KCl (llii) Cl2 (g) + 2KF (llii) a) Which substance in the above equation was; i) oxidised ii) reduced (2 marks) Give an explanation in terms oj electrons for your answers in i) and ii) above (4 marks) b) Which substance can be considered as the; i) oxidising agent ii) reducing agent (2 marks) c) What is the oxidation number of fluorine; i) Before reaction ii) After reaction (2 marks) Question 5: A simple cell changes chemical energy into electrical energy. The cell contains two metallic electrodes in an electrolyte as shown in the diagram. 4

5 voltameter r ! V l------, copper electrode --- dilute sulphuric acid (a) The more reactive metal reacts with the acid and goes into solution as IOns. (i) Which is the more reactive metal in the cell? (1) (ii) Give an ionic half equation to show the more reactive metal fonning IOns. (3) (b) Charged particles move in the outer circuit to the less reactive metal where a gas is fonned. (i) Name the particles that move through the outer circuit. (1) (ii) Name the gas fonned. (1) (c) A graphite rod could be used instead of the copper electrode. Give a reason why this is possible. (2) (d) State whether the voltage ofthe cell would increase, decrease, or stay the same if the zinc electrode was replaced by an iron electrode. Give a reason for your answer. (2) 5

6 Question 6: When a solution of sulphuric acid is electrolysed, using a Hoffmann voltameter, we usually refer to it as the electrolysis of water. a) Draw a labelled diagram of the Hoffmann voltameter. (3) b) Why is, this process called the electrolysis of water? (2) c) Write down all the ions which are present in the solution. (2) d) What is the reaction which occurs at the anode and at the cathode? At the anode: (1) At the cathode: (1) e) Give an indication of the proportion with which the products are produced at their respective electrodes. (1) 6

7 SECTION B ANSWER TWO QUESTION FROM THIS SECTION (Answer this section on the sheets provided) 7. a) Describe briefly, how you would carry out the electrolysis of an aqueous solution of copper (II) sulphate using carbon (inert) electrodes. Your answer should include; i) a labelled diagram, (6) ii) observations you would make at the electrodes and any observations due to a change in solution during electrolysis, (4) ii) equations for the reactions taking place at the electrodes. (4) b) i) Describe the difference in observations (at electrodes and in solution) and in any ofthe electrode reactions if both electrodes are made of copper. ii) State 3 uses of the copper obtained from this process. (6) (20 marks) 8. Aluminum is an impo11ant metal. It is the most abundant metal in the Earth's crust but it does not occur free in nature and is expensive to extract. a) Describe how aluminium is extracted from its purified ores emphasizing the conditions of the electrolyte and the chemical principles. Your answer should include; i) names of the aluminium ores, ii) a simple labelled sketch-diagram of the process, iii) materials from which electrodes are made, iv) half equations at both electrodes. (12) b) Give a reason why the anodes have to be changed from time to time? (2) (b) Give reasons why this extraction process is expensive. (2) (c) Give two different uses of aluminium and, in each case, state the property of the metal on which the use depends. (4) (20 marks) 7

8 9. Iron as a metal, is abundant on Earth. In fact scientists believe that our planet has a core of motel iron. However iron is also found in various ores in the Earth's crust. The history and development of the human race has evolved with iron and its uses. a) Name the two major ores in which iron occurs naturally? (2 marks) b) A huge structure is used industrially for the extraction of iron. What is this structure called? Draw a labelled diagram of this structure. (4 marks) c) During the extraction of iron, two other substances are added. Give the names of these two substances? (2 marks) d) Explain the importance of the substances named in question c) in the extraction process of iron. (2 marks) e) Wlite down the three chemical equations for the chemical reactions occurring during the extraction of iron. (6 marks) f) Much of the iron produced in this process in later used in the production of another substance which happens to be an alloy. i) What is the meaning of the term alloy? ii) Name the alloy into which iron is converted. (2 marks) f) Write down 2 uses of iron in everyday life. (2 marks).,... ;; ', ' (20 marks) 8

9 1 r-'s' BLOCK--/ i 1 I ii, 3 4 Li Periodic table of the elements Key 6" _,.A!Mlll: n:.mber [---1 C- ' -l'-s'"" CNoon-l-r.!I 1Tle!I fori?' J. 2 Be " ,_ L.._._ ' 3 4 l \!ltium 7 a..,tl"'" Na Mg sodium MagIJOol'"' K & """..." c"t I :rr Rb Sr Rub}d\um Sl,ron\!wn Ba im BlIlu:m ' G1 (J,6 Fr Ra FrmruulO AoM (223j J Sc 51d1utn AS 99 V yttrium a9 57 La - B9 Ac. A """.ls LANTHANIDE ELEMENTS A,CT INIDES ELB ENTS Flei;.i!;'Xj :Item!\: '1"-'S5 (I,'l8!!$.',.,; r------transition ELEMENTS Cd' BLOCK)- 2 :z:\ Ti V Cr.M" v... 1_ 4, Ir Nb Mo To lk<olli<m Jtob!um:.."..,... Jjl (96) _m , i 104 f 105 f 1\lt1 i!uncttunp IUnh j i1i''_1 U--'l.U6 Lu I &1 r- Ce Pr. Pm.1:«.. """"".' """"'"" 141). 144 (In 9(1 III 92 i-th Pa 0 Nfl!tJlI!n "- -..,. """""'".Z3.2 (2:1, I 2;18 (7J 26 :v - c_ Io>n CobaJI!Ioe «4$ Fe Co Nt au n Ru Rh Pd. Gd -OJ, '" 72- n - lql "". Hf Ta W Re (J,6 -.. as Ir Pi Au Hg, ld1.., l'tipifji 180 j "* T BLOCK as , ' Sm -----i Eu. Gd. Tb Oy a... -"""""" 94 S!16 ' Pu Am em - Bk Cf. 1Wf -1""" (243) i (U7) iioii'" (2,47) (251)._"--_. 67 Ho Es (254i r.-: BLOC: --- Group'o,1 z 5- ' il- 7 --S B AI... C N a Carbon Nltrogc'ti Oxygen I. 16 SI P S SI1Ic<ln Pho.spboM: Sulphur He Hlli,lum vii '9 10 F,- Ne FilJorioo CI Ar ''1/0' Chlorine Q " : i,rl Ga Ge As Se Gallium B!nNiiIlltI At8eili o Sol,.,m In Sn "" Sb..."" 1:12 83 T e """ Ir.di!.lm T.lk l1a TI Pb 81 P 4 o Thelliuni bid e!smuth -. Jum )9 (21 OJ, 68 fi9 Et Tm. Lu 71 E... 1""," In 17,!; too Fm M<!c No... Lr.-., (:/:\31 (256) { r ImJ I Br Kr 8J'omln IM! SO M I I Xe 100'00 Xenon At Rn _n A'ta.ne ('210) (222)