Skip to content
CIE Jun 2014 v2 Paper 4 Q2
Answers available below
Show answer
Question
1
2
3
4
5
6
7
8
![Lead(II) chloride, PbCl 2, can be used in the manufacture of some types of coloured glass. PbCl 2 is only sparingly soluble in water. The [Pb2+] in a saturated solution of PbCl 2 can be estimated by measuring the cell potential, Ecell, of the following cell. PMT H2(g) 1 atm, 298 K salt bridge saturated solution of PbCl 2 solid PbCl 2 (a) In the spaces below, identify what the four letters A-D in the above diagram represent. ABCD[4] (b) In a saturated solution of PbCl 2, [PbCl 2(aq)] = 3.5102 mol dm3. (i) o for the Pb2+ / Pb electrode is0.13 V. Predict the potential of the right-hand electrode The E in the diagram above. Indicate this by placing a tick in the appropriate box in the table below. electrode potential / V place one tick only in this column0.170.130.09 0.00 Explain your answer.UCLES 2014 9701/42/M/J/14<br />
(ii) Write an expression for the solubility product, Ksp, of PbCl 2.(iii) Calculate the value of Ksp, including units. PMT Ksp =units[5] (c) The behaviours of PbCl 2 and SnCl 2 towards reducing agents are similar, but their behaviours towards oxidising agents are very different. (i) Illustrate this comparison by quoting and comparing relevant E and their ions. Explain what the relative E or reduction of these compounds. o values for the two metals o values mean in terms of the ease of oxidation(ii) Writing a balanced molecular or ionic equation in each case, suggest a reagent to carry out each of the following reactions. the reduction of PbCl 2the oxidation of SnCl 2[5]UCLES 2014 9701/42/M/J/14 [Turn over<br />
PMT (d) (i) Write an equation to represent the lattice energy of PbCl 2. Show state symbols.(ii) Use the following data, together with appropriate data from the Data Booklet, to calculate a value for the lattice energy of PbCl 2. = 349 kJ mol1 electron af nity of chlorine = +195 kJ mol1 enthalpy change of atomisation of lead enthalpy change of formation of PbCl 2(s) = 359 kJ mol1 lattice energy =kJ mol1 (iii) How might the lattice energy of PbCl 2 compare to that of PbBr2? Explain your answer.[6] [Total: 20]UCLES 2014 9701/42/M/J/14<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v2_QP_-_Paper_4_CIE_Chemistry_A-level_2-0.jpg)
![Page 3 Mark Scheme GCE A LEVELMay/June 2014 Syllabus 9701 Paper 42 (a) A: voltmeter or V or potentiometer B: platinum or Pt C: 1 mol dm and H 3 + or HCl (or 0.5 M H2SO4) D: lead (metal) or Pb (b) (i) a (cid:1) in the box next to 0.17 V a comment that the [Pb 2+ 2+ e.g. as [Pb over to the left hand side, or as [Pb reduced ] decreases (from 1 mol dm 2+ ] has decreased plus a description of the outcome,Pb(s) goes (aq) + 2e is less likely to be ] decreases, Pb ), Pb 2+ 2+ 3 (ii) (Ksp =) [Pb 2+ ][Cl] (iii) if [PbCl2] = 3.510 2 so Ksp = (3.510 2 , [Pb 2+ )(7.010 ] = 3.510 2 2 3 2 2 = 1.715 (1.7)104 mol dm )] = 7.010 and [Cl 9 ([2sf) (c) (i) the (M 2+ / M) Eo for the two elements are very similar or are 0.13 and 0.14 V [1] [1] [1] [1] [1] [1] [1] [1] +[1] [1] [1] [1] [1] [1] [1] [3] [1] [1] [Total: 20] Eo (Sn 4+ / Sn 2+ ) = 0.15 V and Eo (Pb 4+ / Pb 2+ ) = 1.69 V so Sn 2+ is quite easily oxidised (to Sn 4+ 4+ 4+ not easily oxidised (to Pb reduced ) or is a stronger reductant or Pb ) or Pb is a stronger oxidant or Pb 2+ is is easily 4+ (ii) e.g. PbCl2 + ZnPb + ZnCl2 (or ionic) (other acceptable reductants: Fe, Mg, Ca but not Na or K) 2+ + Br2Sn Sn + 2Br (other acceptable oxidants: VO 4+ - 2+ , Cr2O7 2 , Ag + , Cl2, Br2, F2, Fe 3+ , MnO4) (d) (i) Pb 2+ (g) + 2Cl(g)PbCl2(s) (ii) Hf = Hat + E(ClCl) + 1 IE + 2EA(Cl) + LE 359 = 195 + 242 + 716 + 14502349 + LE LE = 23493591952427161450 LE = 2264 (kJ mol st IE + 2 nd 1 (iii) LE(PbCl2) > LE(PbBr2) or more exothermic or stronger latticebecause Cl / chloride anion has smaller radius / size than Br / bromideCambridge International Examinations 2014<br />](https://learnah.org/wp-content/uploads/2018/08/June_2014_v2_MS_-_Paper_4_CIE_Chemistry_A-level_2.jpg)