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CIE Nov 2015 v3 Paper 4 Q3
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![Chlorine gas and iron(II) ions react together in aqueous solution as shown. Cl 2(g) + 2Fe2+(aq)2Cl (aq) + 2Fe3+(aq) (a) (i) Complete and label the diagram to show how the standard cell potential, above reaction could be measured at standard conditions. , for the PMT (ii) Use the Data Booklet to calculate the for this reaction. [4] [1] (b) What colour change would you see when chlorine gas is bubbled through a solution containing Fe2+(aq) ions until the reaction is complete?[1] (c) Predict the effect, if any, of decreasing the concentration of Cl (aq) on the magnitude of the cell potential in (a)(ii). Explain your answer.[2]UCLES 2015 9701/43/O/N/15<br />
PMT (d) (i) A fuel cell is an electrochemical cell that can be used to generate electrical energy. In the alkaline hydrogen-oxygen fuel cell, H2(g) and O2(g) are passed over two inert electrodes immersed in an alkaline solution. Write the half-equations for the reactions taking place at each of these electrodes. hydrogen electrodeoxygen electrode[2] (ii) Construct an equation for the overall reaction.[1] (iii) Suggest one possible advantage of using a hydrogen-oxygen fuel cell over a conventional simple cell battery.[1] [Total: 12]UCLES 2015 9701/43/O/N/15 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v3_QP_-_Paper_4_CIE_Chemistry_A-level_3-0.jpg)
![Page 4 Mark Scheme Syllabus Paper Cambridge International A LevelOctober/November 2015 9701 43 Question Marking Point Marks Total Marks (a) (i)Fe and Fe (or suitable compounds), 2 or 3 marking points = [1] 2+ 3+ salt bridge labelled, 4 or 5 marking points = [2] one electrode Pt labelled, one sol 1 mol dm 3 6 or 7 marking points = [3] 8 marking points = [4] PMTCl (or suitable compound), voltmeter, labelled or VCl 2, 1 atm or 298K 2+ 3+ (ii) cell = 1.360.77 = 0.59 V yellow / orange / brown (b) (c) cell voltage increases or becomes more positive / Cl Cl electrode potential increasesCambridge International Examinations 2015 <br />
Page 5 Mark Scheme Syllabus Paper Cambridge International A LevelOctober/November 2015 9701 43 Question Marking Point Marks Total Marks PMT (d) (i) H2 + 2OH2H2O + 2e O2 + 2H2O + 4e4OH (ii) 2H2 + O22H2O (iii) rechargeable / refillable / longer time between charges / longer battery life / less pollution because H2O is the product / O2 can be got from the air (a) (i) sketch graph to show a general decrease in m.p (ii) giant covalent (C or Si) to metal / metallic (Sn or Pb) (b) (i) can react with an acid or base / alkali or can act as an acid or base or has acidic and basic properties (ii) SnO2 + 2NaOHNa2SnO3 + H2O or SnO2 + 2NaOH + 2H2ONa2Sn(OH)6 (c) (i) Cr2O7 2 (Cr2O7 cell = + 1.18 or greater / more positive than Sn 2 / Cr 4+ / Sn ) + 1.33 and E 3+ (Sn 4+ or 2+ ) + 0.15 (ii) 2 Cr2O7 + 3Sn + 14H2 Cr + 3Sn 2+ 3+ 4+ + 7H2O green the same substance gets both oxidised and reduced in the reaction or (d) (i) Ge changes oxid. no. + 2 to 0 and changes oxid. no. + 2 to + 4 (ii) (CN)2 + 2NaOHNaOCN / NaCNO + NaCN + H2OCambridge International Examinations 2015 [Total: 12]<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v3_MS_-_Paper_4_CIE_Chemistry_A-level_3-0.jpg)
