Cells (Electrochemistry) MCQs for CSIR NET GATE - ChemContent

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Chapter: Electrochemistry
Topic: Electrochemical Cells
Content: MCQ Questions & Solutions
Source: CSIR NET, GATE etc. Exams

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Quiz                    PDF

Q1. For the cell

Ag(s) | AgCl(saturated), NaCl(aq,m₁) | NaCl(aq,m₂), AgCl(saturated) | Ag(s)

where m₁ and m₂ are different molalities (m₁>m₂), the standard cell potential is

[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 [B]/[A]
    (c) -ΔG = -ΔGº + 2.303 RT ln [B]/[A]
    (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 + SO₄^2-

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

    Cu⁺(aq) + e^- → Cu(s)         Eº = 0.52 V

    Cu²⁺(aq) + e^- → Cu⁺(aq)     Eº = 0.16 V

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 RT/F
    (c) Eº(M⁺/M) + 2.303 RT/F   
    (d) Eº(M⁺/M) - 2.303 RT/F

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 K_sp 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 log_e (K_sp) 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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