Q94 · CSIR NET Chemistry, December 2011
Paper: CSIR NET December 2011 · Subject: Physical Chemistry · Chapter: Electrochemistry · Topic: Conductance · Marks: 2 · Difficulty: Medium
The overall reaction for the passage of 1.0 faraday of charge in the following cell $\mathrm{Ag}(\mathrm{s})-\mathrm{AgCl}(\mathrm{s})\left|\mathrm{KCl}\left(\mathrm{a}_{1}\right)\right| \mathrm{KCl}\left(\mathrm{a}_{2}\right) \mid \mathrm{AgCl}(\mathrm{s})-\mathrm{Ag}(\mathrm{s})$ is given by (t denotes the transport numbers)
(a)$\mathrm{t}_{+} \mathrm{KCl}\left(\mathrm{a}_{1}\right) \rightarrow \mathrm{t}_{+} \mathrm{KCl}\left(\mathrm{a}_{2}\right)$
(b)$\mathrm{t}_{+} \mathrm{KCl}\left(\mathrm{a}_{2}\right) \rightarrow \mathrm{t}_{+} \mathrm{KCl}\left(\mathrm{a}_{1}\right)$
(c)$\mathrm{t}_{-} \mathrm{KCl}\left(\mathrm{a}_{1}\right) \rightarrow \mathrm{t}_{-} \mathrm{KCl}\left(\mathrm{a}_{2}\right)$
(d)$\mathrm{t}_{-} \mathrm{KCl}\left(\mathrm{a}_{2}\right) \rightarrow \mathrm{t}_{-} \mathrm{KCl}\left(\mathrm{a}_{1}\right)$
Answer
Answer: B ✓ checked by 4AB · confidence medium
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
With Ag/AgCl electrodes reversible to Cl⁻, passage of 1 F moves t₊ mol of KCl across the junction from the more concentrated to the more dilute solution: t₊ KCl(a₂) → t₊ KCl(a₁) (the cell is spontaneous for a₂ > a₁).
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