ELECTROCHEMISTRY EXERCISE – I Q.1 UNSOLVED PROBLEMS In the buton cell widely used in watches and other devices, the following reaction takes place Zn(s) + AgO(s) + H2O(l)  Zn2+ (aq) + 2Ag(s) + 2OH–(aq) Determine rGº and Eº for the reaction. Q.2 Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration. Q.3 The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 S cm–1. Calculate its molar conductivity. Q.4 How much charge is required from the following reductions: (i) 1 mol of Al3+ to Al (ii) 1 mol of Cu2+ to Cu? (iii) 1 mol of MnO4– to mn2+? Q.5 A solution of Ni(NO3)2 is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode? Q.6 Three electrolytic cells A, B, C containing solution of ZnSO4, AgNO3 and CuSO4, respectively are connected in series. A steady current of 1.5 amperes are passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow ? What mass of copper and of zinc were deposited? Q.7 What is the function of salt bridge in electrochemical cells? Q.8 At infinite dilution, the molar conductance of Na+ and SO42– ions are 50 S cm2 mol–1 and 160 Scm2 mol–1 respectively. What will be the molar conductance of sodium sulphate at infinite dilution? Q.9 Which will have greater molar conductivity? "Solution having 1 mol of KCl in 200 cc or 1 mol of KCl in 600 cc." Q.10 What are secndary cels? Give the anode or cathode reaction of Nickel -Cadmium storage cell. Q.11 What is corrosion ? How is cathodic protection of iron different from its galvanisation? Q.12 What do you mean by e.m.f. of a cell. Calculate the e.m.f. of the cell Mg(s) |Mg2+(0.2 M) ||Ag+(1 ×10– 3M)|Ag, Eo to 0.1 M. Ag / Ag o = 0.80 V, EMg2 / Ag = –2.37V, What will be the effect on e.m.f., if conc. of Mg2+ is decreaed