a) The following reactions can occur at the cathode during the electrolysis of aqueous silver chloride solution: $$\mathrm{Ag^+(aq)+e^-\longrightarrow Ag(s)},\quad E^{\circ}=+0.80\ \mathrm{V}$$ $$\mathrm{H^+(aq)+e^-\longrightarrow \tfrac{1}{2}H_2(g)},\quad E^{\circ}=0.00\ \mathrm{V}$$ On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why? b) Define limiting molar conductivity. Why does the conductivity of an electrolyte solution decrease with a decrease in concentration?

(a) Ag⁺ reduction — the species with the higher reduction potential is discharged first. (b) Λ°_m = molar conductivity as C→0; on dilution there are fewer ions per unit volume, so κ falls.

CBSE Class 12 · 2015 · Delhi · Redox Reactions and ElectrochemistryShort Answer

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a) The following reactions can occur at the cathode during the electrolysis of aqueous silver chloride solution:

A g^{+} (aq) + e^{-} ⟶ Ag (s), E^{\circ} = + 0.80 V

H^{+} (aq) + e^{-} ⟶ \frac{1}{2} H_{2} (g), E^{\circ} = 0.00 V

On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why?
b) Define limiting molar conductivity. Why does the conductivity of an electrolyte solution decrease with a decrease in concentration?

Solution

(a) At the cathode, the species with the higher reduction potential is reduced preferentially. Since

E^{\circ} (A g^{+} /Ag) = + 0.80

> E^{\circ} (H^{+} / H_{2}) = 0.00

V, silver ions are reduced and Ag is deposited.
(b) Limiting molar conductivity (

Λ_{m}^{\circ}

) is the molar conductivity of the solution as its concentration approaches zero (infinite dilution).
Conductivity measures the conductance of ions in a unit volume; on decreasing the concentration (dilution), the number of ions per unit volume falls, so the conductivity decreases.

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CBSE Class 12 · 2015 · Delhi · Redox Reactions and ElectrochemistryShort Answer

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