Engineering Chemistry S Datta

264 ENGINEERING CHEMISTRY
20. Distinguish: (i) a reversible cell from an irreversible cell
(ii) a galvanic cell from a concentration cell.
21. What is Nernst equation? State its utility.
22. Derive an expression for electrode potential of an M/M n+ electrode?
23. What is fuel cell? Give detail of one such cells.
24. What are reversible and irreversible cells?
25. Explain the construction of Ni-Cd cell.
26. Give the cell reaction of the following:
(i) Zn +2 /Zn, (ii) AgCl(s), Cl – /Ag, (iii) Fe +3 /Fe +2 Pt, (iv) 2H + /H 2
(g) Pt.
27. Give the use of Ag-AgCl electrode.
28. Describe the construction and working of Daniel cell.
29. Explain the construction and working of lead storage battery.
30. How is single electrode potential measured experimentally?
31. Write down the electrode reactions and overall cell reactions for the following cells. Also give the
expression for their e.m.f.
(i) Zn | ZnSO 4
|| CuSO 4
/Cu
(ii) (Pt) H 2
(1 atm) | HCl/AgCl(s), Ag
32. Describe the potentiometric methods for
(i) Determination of pH of a solution.
(ii) Calculation of solubility product of AgCl.
33. The reaction H 2
+ Cl 2
+ 2H 2
O 2H 2
O + 2Cl – has an equilibrium constant K = 10 46 at 25°C.
Calculate E° at 25°C for cell: (Pt) H 2
/HCl (aq)/Cl 2
(Pt).
34. The standard potentials of Cu/Cu +2 and Cu/Cu + system are 0.337 and 0.530 V, respectively. Give
the equilibrium constant for the reaction,
2Cu + Cu 2+ + Cu
35. Zinc rod is dipped in 0.01 (M) ZnSO 4
solution at 25°C. Give the single electrode potential of Znhalf
cell, if
E° cell
= + 0.763 V (0.8192 V)
36. Calculate the e.m.f. of voltaic cell: Fe | Fe +2 (aq) || Cu +2 (aq) | Cu. Given the electrode potentials of
Cu and Fe are 0.34 V and –0.44 V, respectively. (0.78 V).
37. Will a reaction take place if an Ag-bar is placed in a solution of FeSO 4
? Explain using the following
data:
∈° +
Ag / Ag
= 0.799 V, and ∈° + 2 = 0.44 V (– 1.239 V)
Fe
/Fe
38. Calculate the e.m.f. of a Daniel cell at 25°C, when the concentrations of ZnSO 4
and CuSO 4
are
0.001 M and 0.1 M respectively. The standard potential of the cell is 1.1 V (1.13 V).
39. Calculate the e.m.f of the following concentration cell:
Ag/Ag + (0.1 M) || Ag + (1M) | Ag [Ans. 0.0592 V]
40. The e.m.f. of the cell at 25°C
Hg(l) | Hg 2
Cl 2
(s), KCl(sol) (1.0 N)| Quinhydrone | Pt
is 0.212 V. Calculate the pH of the solution. The potential of the normal calomel electrode is
0.2812 V and E° for the quinhydrone electrode is 0.6996 V, both at the same temperature.
[Ans. 6.5]