Chapter: Electrochemistry
Topic: Electrochemical Cells
Content: MCQ Questions & Solutions
Source: CSIR NET, GATE etc. Exams
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Q1. For the cell
Ag(s) | AgCl(saturated), NaCl(aq,m1) | NaCl(aq,m2), AgCl(saturated) | Ag(s)
[GATE 2001]
(a) -RT ln (m1/m2)
(b) zero
(c) -RT ln (a1/a2)
(d) -FRT ln (a1)
Q2. The
Nernst equation for the reaction, A2+ + 2e- → B, in terms of the free
energy change is
[GATE 2002]
(a) ΔG = ΔGº + 2.303 RT ln [B]/[A]
(b) ΔG = ΔGº - 2.303 RT ln
(c) -ΔG = -ΔGº + 2.303 RT ln
(d) ΔG = -ΔGº + 2.303 RT ln [B]/[A]
Q3. For
the reaction, Hg2Cl2(s) + H2(g) → 2 Hg(l) + 2 HCl(aq), the correct representation of the cell
and the thermodynamic properties ΔG, ΔH and ΔS at 298 K respectively, are
(given: E298 = 0.2684 V and temperature coefficient = -3 x 10-4 V K-1)
[GATE 2003]
(a) Pt | H2(g, 1 atm) | HCl(aq) | Hg2Cl2(s)
| Hg(l)
ΔG = -51.8 kJ
mol-1, ΔH = -69 kJ mol-1, ΔS = -58 J K-1 mol-1
(b) Pt | H2(g, 1 atm) | HCl(aq) | Hg2Cl2(s)
| Hg(l)
ΔG = -25.9 kJ
mol-1, ΔH = -34.5 kJ mol-1, ΔS = -29 J K-1 mol-1
(c) Hg(l) | Hg2Cl2(s) | HCl(aq) | H2(g,
1 atm) | Pt
ΔG = -51.8 kJ
mol-1, ΔH = -69 kJ mol-1, ΔS = 58 J K-1 mol-1
(d) Hg(l) | Hg2Cl2(s) | HCl(aq) | H2(g,
1 atm) | Pt
ΔG = 51.8 kJ
mol-1, ΔH = 69 kJ mol-1, ΔS = 58 J K-1 mol-1
Q4. From
the data of two half-cell reactions:
AgCl(s) + e- → Ag(s) + Cl-(aq) Eº = +0.22 V
Ag+(aq) + e- → Ag(s) Eº = +0.80 V
[GATE 2004]
(a) 1.5 x 10-10
(b) 2.1 x 10-7
(c) 3.0 x 10-3
(d) 1.2 x 10-5
Q5. The
solubility product of silver sulphate at 298 K is 1.0 x 10-5. If the
standard reduction potential of the half-cell
Ag+ +
e- → Ag
is 0.80 V, the standard reduction
potential of the half-cell
Ag2SO4 + 2 e- → 2 Ag + SO42-
is:
[GATE 2004]
(a) 0.15 V
(b) 0.22 V
(c) 0.65 V
(d) 0.95 V
Q6. Given
the standard potential for the following half-cell reaction at 298 K
Calculate the ΔGº (kJ) for the reaction,
2 Cu+(aq) →
Cu(s) + Cu2+,
[GATE 2006]
(a) -34.740
(b) -65.720
(c) -69.480
(d) -131.440
Q7. Given
that Eº(Fe3+/Fe) = -0.04 V and Eº(Fe2+/Fe) = -0.44 V, the
value of Eº(Fe3+/Fe2+) is:
[GATE 2007]
(a) 0.76 V
(b) -0.40 V
(c) -0.76 V
(d) 0.40 V
Q8. The standard reduction potential at 298 K for single electrodes are given below
Electrode Electrode Potential
Mg2+/Mg -2.34 V
Zn2+/Zn -0.76 V
Fe2+/Fe -0.44 V
From this we can infer that
[GATE 2010]
(a) Zn can reduce both Mg2+ and Fe2+
(b) Fe can reduce both Zn2+ and Mg2+
(c) Mg can reduce both Zn2+ and Fe2+
(d) Mg can reduce Zn2+ but not Fe2+
Q9. For
the concentration cell
M | M+(aq,
0.01 mol dm-3) || M+(aq, 0.1 mol dm-3) | M
The EMF (E) of the cell at temperature (T) equals
[GATE 2011]
(a) 2.303 RT/F
(b) -2.303
(c) Eº(M+/M) + 2.303 RT/F
(d) Eº(M+/M) - 2.303
Q10. At
298 K, the EMF of the cell
Pt | H2
(1 bar) | H+ (solution) || Cl- | Hg2Cl2
| Hg
Is 0.7530 V. The standard potential of the calomel
electrode is 0.2802 V. If the liquid junction potential is zero, the pH of
solution is:
[GATE 2012]
(a) 4.7
(b) 7.4
(c) 8.0
(d) 12.7
Q11. For the
following reaction
2 MnO4-
+ 5 H2C2O4 + 6 H+ → 2 Mn2+ + 8 H2O + 10 CO2
Eº(MnO4-/Mn2+)
= +1.51 V and Eº(CO2/H2C2O4) =
-0.49 V. At 298 K, the equilibrium constant is:
[GATE 2012]
(a) 10500
(b) 10338
(c) 1038
(d) 10833
For Q12 & 13:
The standard half cell potential of Fe3+(aq) | Fe
is -0.036 V and that of OH-(aq) | Fe(OH)3(s) | Fe is
-0.786 V
Q12. For the determination of
solubility product Ksp of Fe(OH)3, the appropriate cell
representation and its EMF are, respectively.
[GATE 2013]
(a) Fe | Fe(OH)3(s) | OH-(aq) Fe3+(aq)
| Fe, -0.750 V
(b) Fe | Fe3+(aq) OH-(aq) | Fe(OH)3(s) | Fe,
-0.750 V
(c) Fe | Fe(OH)3(s) | OH-(aq) Fe3+(aq) | Fe,
+0.750 V
(d) Fe | Fe3+(aq) OH-(aq) | Fe(OH)3(s) | Fe,
-0.822 V
Q13. The value loge (Ksp) for Fe(OH)3
at 298 K is
[GATE 2013]
(a) -38.2
(b) +87.6
(c) -96.0
(d) -87.6
Q14. A
platinum electrode is immersed in a solution containing 0.1 M Fe2+
and 0.01 M Fe3+. Its potential is found to be 0.77 V against SHE.
Under standard conditions and considering activity coefficients to be equal to
unity, the potential of the electrode, when the concentration of Fe3+
is increased to 1 M, is ______
[GATE 2014]
Q15. Given
the Eº values for the following reaction sequence
the compound value of Eº for Mn6+
→ Mn2+ (in volts) is
_____
[GATE 2015]
Q16. The solubility product of
AgBr(s) is 5 x 10-13 at 298 K. If the standard reduction potential
of the half-cell Eº(Ag|AgBr(s)/Br-) is 0.07 V, the standard
reduction potential Eº(Ag+/Ag) is ____ volts.
[GATE 2015]
Q17. The titration of a strong
acid with a strong base is represented by the plot
[GATE 2016]
Answer Key
Q1.b Q2.a Q3.a Q4.a Q5.c Q6.a Q7.a Q8.c Q9.a Q10.c Q11.b Q12.b Q13.d
Q14.=~0.83
Q15.=~1.66
Q16.=~0.796
Q17.c
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