QJEEM12Chcce2: JEE Main 2012 Chemistry - Class 12 JEEM12Chcce2 Solution: The standard reduction potentials for Zn 2+ / Zn, Ni 2+ / Ni,…

Question

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The standard reduction potentials for Zn²⁺/ Zn, Ni²⁺/ Ni, and Fe²⁺/ Fe are –0.76, –0.23 and –0.44 V respectively. The reaction

X + Y²⁺

\to

X²⁺ + Y will be spontaneous when :

Accepted Answer

For a spontaneous reaction

Δ G

must be

- v e

Since

Δ G = - n F E^{\circ}

Hence for

Δ G

to be

- v e

Δ E^{\circ}

has to be positive.

Which is possible when

X = Z n, Y = N i

Z n + N i^{+ +} \overset{}{⟶} Z n^{+ +} + N i

E_{Z n / Z n^{+ 2}}^{\circ} + E_{N i^{2 +} / N i}^{\circ}

= 0.76 + (- 0.23) = + 0.53

(positive).

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