JEE Main 2026 — Chemistry Physical Chemistry

2026integermedium

Consider the following electrochemical cell at 298 K

$\mathrm{Pt}\left|\mathrm{HSnO}_{2}{ }^{-}(\mathrm{aq})\right| \mathrm{Sn}(\mathrm{OH})_{6}{ }^{2-}(\mathrm{aq})\left|\mathrm{OH}^{-}(\mathrm{aq})\right| \mathrm{Bi}_{2} \mathrm{O}_{3}(\mathrm{~s}) \mid \mathrm{Bi}(\mathrm{s})$ .

If the reaction quotient at a given time is $10^{6}$ , then the cell EMF ( $\mathrm{E}_{\text {cell }}$ ) is $\_\_\_\_$ $\times 10^{-1} \mathrm{~V}$ (Nearest integer).

Given the standard half-cell reduction potential as

$\mathrm{E}_{\mathrm{Bi}_{2} \mathrm{O}_{3} / \mathrm{Bi}, \mathrm{OH}^{-}}^{\circ}=-0.44 \mathrm{~V} \text { and } \mathrm{E}_{\mathrm{Sn}(\mathrm{OH})_{6}^{2-} / \mathrm{HSnO}_{2}^{-}, \mathrm{OH}^{-}}^{\circ}=-0.90 \mathrm{~V}$

Official previous-year question

Held on 22 Jan 2026 · Verified 6 Jul 2026.

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Solution

The electrochemical cell has cathode:

$Bi_2O_3 + 3H_2O + 6e^- \rightarrow 2Bi + 6OH^-$ with $E° = -0.44$ V

and anode:

$Sn(OH)_6^{2-} - 2e^- \rightarrow HSnO_2^- + H_2O + OH^-$ with $E° = -0.90$ V.

The standard cell EMF is $E°_{cell} = -0.44 - (-0.90) = 0.46$ V.

Using the Nernst equation with $Q = 10^6$ and $n = 6$ electrons transferred:

$E_{cell} = 0.46 - \frac{0.059}{6} \log(10^6) = 0.46 - \frac{0.059 \times 6}{6} = 0.46 - 0.059 = 0.401$ V.

Expressing as $x \times 10^{-1}$ V:

$0.401 = 4.01 \times 10^{-1}$ V, so $x = 4$ (nearest integer).

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Solution

The electrochemical cell has cathode:

$Bi_2O_3 + 3H_2O + 6e^- \rightarrow 2Bi + 6OH^-$ with $E° = -0.44$ V

and anode:

$Sn(OH)_6^{2-} - 2e^- \rightarrow HSnO_2^- + H_2O + OH^-$ with $E° = -0.90$ V.

The standard cell EMF is $E°_{cell} = -0.44 - (-0.90) = 0.46$ V.

Using the Nernst equation with $Q = 10^6$ and $n = 6$ electrons transferred:

$E_{cell} = 0.46 - \frac{0.059}{6} \log(10^6) = 0.46 - \frac{0.059 \times 6}{6} = 0.46 - 0.059 = 0.401$ V.

Expressing as $x \times 10^{-1}$ V:

$0.401 = 4.01 \times 10^{-1}$ V, so $x = 4$ (nearest integer).

JEE Main 2026 — Chemistry Physical Chemistry

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JEE Main 2026 — Chemistry Physical Chemistry

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JEE Main Physical Chemistry in other years

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