For the cell reaction 2Fe^3+(aq) + 2I^-(aq) -> 2Fe^2+(aq) + I2(aq), E^ cell = 0.24 V at 298 K. The standard Gibbs energy ( _r G^°) of the cell reaction is:

Correct answer: (B) -23.16 kJ,mol-1. Answer: (B) -23.16 kJ,mol-1 (as per official key, n=1) Solution: _r G^° = -nFE^ cell. The official key takes n = 1: _r G^° = -1 × 96500 × 0.24 = -23160 J -23.16 kJ,mol-1 (option B). However, the printed balanced reaction transfers 2 electrons (Fe^3+ -> Fe^2+ for 2 Fe). With n = 2: _r G^° = -2 × 96500 × 0.24 = -46320 J -46.32 kJ,mol-1 (option A). The physically correct value for the reaction as written is option A; the answer is retained as the official key (B) with this n-ambiguity flagged.

NEET 2019 · ChemistryPrevious Year Question

For the cell reaction $2 Fe X^{3 +} (aq) + 2 I X^{-} (aq) 2 Fe X^{2 +} (aq) + I X_{2} (aq)$ , $E_{ce l l}^{\circ} = 0.24 V$ at $298 K$ . The standard Gibbs energy ( $Δ_{r} G^{\circ}$ ) of the cell reaction is:

Answer: (B) $- 23.16 k J m o l^{- 1}$ . \textbf{Answer:} (B) $- 23.16 k J m o l^{- 1}$ (as per official key, $n = 1$ ) \textbf{Solution:} $Δ_{r} G^{\circ} = - n F E_{ce l l}^{\circ}$ .

A. $- 46.32 k J m o l^{- 1}$
B. $- 23.16 k J m o l^{- 1}$ ✓
C. $46.32 k J m o l^{- 1}$
D. $23.16 k J m o l^{- 1}$

Correct Answer

(B) $- 23.16 k J m o l^{- 1}$

Solution & Explanation

\textbf{Answer:} (B) $- 23.16 k J m o l^{- 1}$ (as per official key, $n = 1$ ) \textbf{Solution:} $Δ_{r} G^{\circ} = - n F E_{ce l l}^{\circ}$ . The official key takes $n = 1$ : $Δ_{r} G^{\circ} = - 1 \times 96500 \times 0.24 = - 23160 J \approx - 23.16 k J m o l^{- 1}$ (option B). However, the printed balanced reaction transfers $2$ electrons ( $Fe X^{3 +} Fe X^{2 +}$ for $2$ Fe). With $n = 2$ : $Δ_{r} G^{\circ} = - 2 \times 96500 \times 0.24 = - 46320 J \approx - 46.32 k J m o l^{- 1}$ (option A). The physically correct value for the reaction as written is option A; the answer is retained as the official key (B) with this n-ambiguity flagged.

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For the cell reaction 2FeX3+(aq)+2IX−(aq)​2FeX2+(aq)+IX2​(aq), Ecell∘​=0.24 V at 298 K. The standard Gibbs energy (Δr​G∘) of the cell reaction is:

Solution & Explanation

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For the cell reaction $2 Fe X^{3 +} (aq) + 2 I X^{-} (aq) 2 Fe X^{2 +} (aq) + I X_{2} (aq)$ , $E_{ce l l}^{\circ} = 0.24 V$ at $298 K$ . The standard Gibbs energy ( $Δ_{r} G^{\circ}$ ) of the cell reaction is: