Following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:
$N a^{+} (a q) + e^{-} \to N a (s) E^{0} = - 2.71 V$
$H^{+} (a q) + e^{-} \to \frac{1}{2} H_{2} (g) E^{0} = 0.00 V$
On the basis of their standard reduction electrode potential $(E^{0})$ values, which reaction is feasible at the cathode and why?

(b) Why does the cell potential of mercury cell reamin constant throughout its life?

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Solution

(a) Since the standard reduction potential of second reaction is greater than first reaction, the second reaction is feasible at cathode (reduction occurs at cathode).
i.e., $H^{+} (a q) + e^{-} \to \frac{1}{2} H_{2} (g), E^{0} = 0.00 V .$

(b) In the mercury cell, as the overall redox reaction (i.e., $Z n (s) + H g O (s) \to Z n O (s) + H g (l))$ does not involve any ion whose concentration may change, the cell potential of mercury cell remains constant throughout its life.

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Similar questions

(a) Following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:

$N a^{+} (a q) + e^{-} \to N a (s) E^{\circ} = - 2.71 V$
$H^{+} (a q) + e^{-} \to \frac{1}{2} H_{2} (g) E^{\circ} = 0.00 V$

On the basis of their standard reduction electrode potential $(E^{\circ})$ values, which reaction is feasible at the cathode and why?

(b) Why does the cell potential of mercury cell remain constant throughout its life?

N a^{+} (a q) + e^{-} \to N a (s) E^{0} = - 2.71 V

H^{+} (a q) + e^{-} \to \frac{1}{2} H_{2} (g) E^{0} = 0.00 V

(E^{0})

{N a}^{+} (a q) + e^{-} ⟶ N a (s) E^{0} = - 2.71 V

H^{+} (a q) + e^{-} ⟶ \frac{1}{2} H_{2} (g) E^{0} = 0.00 V

(E^{0})

A g^{+} (a q) + e \to A g (s) E^{\circ} = + .80 V

H^{+} (a q) + e^{-} \to \frac{1}{2} H_{2} (g) E^{o} = 0.00 V

(E^{o})

C u S O_{4}

C u^{+ 2} + 2 e^{-} \to C u

C u \to C u^{+ 2} + 2 e^{-}

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