Whitley Prelim Answers

1B

2B

3A

4C

5B

6D

7C

8B

9B

10 C

11 B

12 C

13 A

14 B

15 C

16 C

17 A

18 C

19 A

20 D

21 D

22 A

23 A

24 D

25 D

26 A

27 D

28 C

29 B

30 C

31 D

32 A

33 B

34 C

35 D

36 C

37 C

38 C

39 A

40 B

Section A A1 (a) (i) A copper; (ii) B copper (II) oxide; (iii) C copper (II) sulphate; (iv) D carbon dioxide; [4] (b) Neutaralisation; (c) Transistion; (d) zinc; a more reactive metal than copper can displace it from copper (II) sulphate solution; (e) CuSO4 + Zn  Cu + ZnSO4; [5] A2 (a) (i) aluminium, iron; (ii) fluorine, chlorine; (iii) magnesium and fluorine; (iv) carbon and chlorine or fluorine (v) chlorine, fluorine; [5] (b) Drawing consists of magnesium ion circle with 8 crosses and charge 2+; Fluoride or chloride ions two circles of 7 dots and one cross and one negative charge. [2] A3 (a) bromine gas or chlorine gas or nitrogen dioxide gas; [1] (b) (i) by photochemical reaction between nitrogen dioxide and oxygen gas; (ii) It produces peroxyacyl nitrates PAN – photochemical smog which causes tearing of the eye or in high concentration triggers asthmatic attacks; [2] (c) Describes energy being absorbed during a reaction; [1]

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(d) The energy absorbed in breaking the oxygen bonds; is greater; than the energy evolved in the forming bonds to give ozone [2] (e) PbS(s) + 2O3(g)  PbSO4(s) + O2(g) ; lead (II) sulphide is oxidized to PbSO4; when the oxidation state of S is increased from – 2 to + 6; [3]

A4 (a) potassium sulphate; (b) 4OH –  2H2O + O2 + 4 e – ; (c) copper will be oxidisied to copper(II) oxide by oxygen gas liberated at the anode; (d) (i) CUSO4:no hydrogen gas but metal copper will be deposited at the cathode; (ii) NaI:no oxygen gas but iodine vapour will be liberated at the anode; [5] A5 (a) 1mol citric acid + 3moles KOH  1mol potassium citrate + 3mol water; Structure of sodium citrate: the three acidic H are replaced by three potassium atoms; [2] (b) 1mol citric acid reacts with 3 mols potassium hydroxide 0.0350 mol citric acid reacts with 0.105 mols of KOH; M x V = 0.105 mol KOH V = 0.105/0.1 = 1.05 dm3 KOH;

[2]

(c) H+ + OH -  H2O;

[1]

A6 (a) In paraffin oil; [1] (b) (i) 2Q + Cl2  2QCl; [1] (ii) Vigorous reaction of white flash of light; white fumes condensed as white solid on side of vessel; [2] (c) by electrolysis of molten Q chloride; using carbon electrodes; [2] (d) vigorous reaction o Q darting about on the surface of the solution or effervence; and a blue precipitate forms; [2] A7 (a) Addition; (b) poly(methyl methacrylate); H CH3 H CH3 H CH3 I I I I I I (c) - C – C – C – C – C – C – I I I I I I H H H H H H (d) Mr methylmethacrylate = 100; No. of monomers = 960000 / 100 = 9600;

[1] [1]

[2]

[2]

2

(c) the polymermer does not shatter like glass in a crash; Section B B8 (a)

[1]

(i)

n = 2; because the percentage of C in C2H6O = 24/46 x 100% = 52.2% (ii) the isomers are propan- 1-ol; and propan -2-ol; all covalent bonds must be shown

(b) Crack heptane using catalyst at a high temperature; Addition reaction between propene and steam; Phosphoric acid (catalyst), at 300 oC, 70 atmospheres; C7H16  C3H6 + C4H10; C3H6 + H2O  C3H7OH; (c) Add silver nitrate solution follow by nitric acid; HCl gives a white precipitate but not ethanoic acid;

[1] [2]

[5]

[2]

B9 (a) (i) 1:14.3 (ii) After travelling for a distance, the car engine is hot; nitrogen and oxygen from the air for reacting with the fuel in the engine, react to form nitric oxide; (iii) nitrogen and carbon dioxide; 2NO + 2CO  2CO2 + N2; [5] (b) (i) Na+, OH-, H+; (ii) H2 + 2OH -  2H2O + 2 e- ; (iii) oxidation, as there is a loss of electrons; (iv) in order to balance the flow of electrons leaving and entering the cell the overall reaction is: 2H2 + O2  2H2O two volumes hydrogen and one volume of oxygen must be fed into the cell; (v) 2.4 dm3 hydrogen; [5]

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Either B10 (a) The blue colour of copper (II) sulphate solution will fade or turn colourless; Zn will be coated with a layer of brown substance; The rod AB will dip at B; [3] (b) (i) aluminium and iron(III) oxide; (ii) the mixture will turn red hot or molten brown liquid form; a white ash will also form; (iii) magnesium oxide and copper; (iv) add excess sulphuric acid to dissolve all magnesium oxide; filter the mixture to collect copper (residue); rinse the copper with distilled water to remove soluble insolubilities.

[1] [2] [1]

[3]

Or B11 (a) Catalyst – a substance that increases the rate of a reaction but remains chemically unchanged; It also lowers the activation energy of a reaction, so that many more molecules can react at a lower energy; [2] (b) Increase in temperature increases the KE of the reacting molecules and they move at higher speed; the molecules will hence collide more frequently and more forcefully leading to a rise in the rate of reaction; [2] (c)

NO – double the concentration, increases the rate four times; CO – increase in concentration does not increase the rate; O2 – increase in concentration does not incrase the rate;

[3]

(d) Zinc displaces copper from copper (II) sulphate The copper deposited on the zinc surface acts as a catalyst; Zn + CuSO4  Cu + ZnSO4 1.00g of Zn = 1/65 mol, 5 g of CuSO4 = 5/160 CuSO4 will be in excess; all zinc will be reacted completely, and none left for reaction with the sulphuric acid;

[3]

4