The efficiency of a fuel cell is given by:

$\left(\mathrm{a}\right) ∆\mathrm{H}/∆\mathrm{G} \left(\mathrm{b}\right) ∆\mathrm{G}/∆\mathrm{S}$
$\left(\mathrm{c}\right) ∆\mathrm{G}/∆\mathrm{H} \left(\mathrm{d}\right) ∆\mathrm{S}/∆\mathrm{G}$

A hypothetical electrochemical cell is shown below A l A⁺ (xM)l l B⁺ (yM) l B
The Emf measured is +0.20 V.The cell reaction is:-
(1) A⁺ + B → A + B⁺

(2) A⁺ + e^- →  A ; B⁺ + e^- → B

(3) the cell reaction cannot be predicted

(4) A + B⁺ → A⁺ + B

The E° in the given diagram is,

(1) 0.5

(2) 0.6

(3) 0.7

(4) 0.8

At 298K the standard free energy of formation of H₂O(l) is –237.20kJ/mole while that of its ionisation into H+ iion and hydroxyl ions is 80 kJ/mole, then the emf of the following cell at 298 K will be

H₂(g,1 bar) | H⁺ (1M) || OH^–(1M) | O₂ (g, 1bar)

(1) 0.40 V

(2) 0.81 V

(3) 1.23 V

(4) –0.40 V

Which of the following cell can produce more electric work.

(1) pt,H₂|NH₄Cl||0.1MCH₃COOH|H₂,pt

(2) pt,H₂|0.1MHCl||0.1MNaOH|H₂,pt

(3) pt,H₂|0.1MHCl||0.1MCH₃COOK|H₂,pt

(4) pt,H₂|0.1MCH₃COOK||0.1MHCl|H₂,pt

At what $\frac{\left[{\mathrm{Br}}^{\mathrm{-}}\right]}{\sqrt{\left[{\mathrm{CO}}_3^{2-}\right]}}$ does the following cell have its reaction at equilibrium?

Ag(s) | Ag₂CO₃(s) | Na₂CO₃ (aq) || KBr(aq) | AgBr(s) | Ag(s)

K_SP = 8 × 10^–12 for Ag₂CO₃ and K_SP = 4 × 10^–13 for AgBr

(1) $\sqrt{1}$ × 10^–7

(2) $\sqrt{2}$ × 10^–7

(3) $\sqrt{3}$ × 10^–7

(4) $\sqrt{4}$ × 10^–7

It is observed that the voltage of a galvanic cell using the reaction M(s) + xH⁺ $\underset{}{\overset{}{\to }}$ M^x+ + $\frac{x}{2}$ H₂ varies linearly with the log of the square root of the hydrogen pressure and the cube root of the M^x+ concentration. The value of x is:

1. 2

2. 3

3. 4

4. 5

Acetic acid has K_a = 1.8 × 10^–5 while formic acid had K_a = 2.1 × 10^–4. What would be the magnitude of the emf of the cell

Pt(H₂) $\left|\begin{array}{l}0.1\mathrm{M} \mathrm{acetic} \mathrm{acid}+\\ 0.1\mathrm{M} \mathrm{sodium} \mathrm{acetate}\end{array}\right|\left|\begin{array}{l}0.1\mathrm{M} \mathrm{formic} \mathrm{acid}+\\ 0.1\mathrm{M} \mathrm{sodium} \mathrm{formate}\end{array}\right|$ Pt(H₂) at 25°C

(1) 0.0315 volt

(2) 0.0629 volt

(3) 0.0455 volt

(4) 0.0545 volt

Consider the cell Ag(s)|AgBr(s)|Br–(aq)||AgCl(s)|Cl–(aq)|Ag(s) at 25°C. The solubility product constants of AgBr & AgCl are respectively 5 × 10^–13 & 1 × 10^–10. For what ratio of the concentrations of Br^– & Cl^–ions would the emf of the cell be zero ?

(1) 1 : 200

(2) 1 : 100

(3) 1 : 500

(4) 200 : 1

Calculate the useful work of the reaction Ag(s) + 1/2Cl₂(g) $\underset{}{\overset{}{\to }}$ AgCl(s)

Given $\mathrm{E}{°}_{\mathrm{Cl}2/{\mathrm{Cl}}^{–}} = + 1.36 \mathrm{V}, \mathrm{E}{°}_{\mathrm{AgCl}/\mathrm{Ag},{\mathrm{Cl}}^{–}} = 0.22 \mathrm{V}$

If ${\mathrm{P}}_{{\mathrm{Cl}}_2}$ = 1 atmand T = 298 K

(1) 110 kJ/mol

(2) 220 kJ/mol

(3) 55kJ/mol

(4) 1000 kJ/mol