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Question: Answered & Verified by Expert
The standard reduction potentials for $\mathrm{Zn}^{2+} / \mathrm{Zn}, \mathrm{Ni}^{2+} / \mathrm{Ni}$, and $\mathrm{Fe}^{2+} / \mathrm{Fe}$ are $-0.76,-0.23$ and $-0.44 \mathrm{~V}$ respectively. The reaction $\mathrm{X}+\mathrm{Y}^{2+} \rightarrow \mathrm{X}^{2+}+\mathrm{Y}$ will be spontaneous when:
ChemistryElectrochemistryJEE MainJEE Main 2012 (Offline)
Options:
  • A
    $X=N i, Y=F e$
  • B
    $X=N i, Y=Z n$
  • C
    $X=F e, Y=Z n$
  • D
    $X=Z n, Y=N i$
Solution:
2298 Upvotes Verified Answer
The correct answer is:
$X=Z n, Y=N i$
$\begin{aligned}
& \mathrm{Zn}+\mathrm{Fe}^{+2} \rightarrow \mathrm{Zn}^{+2}+\mathrm{Fe} \\
& \mathrm{Fe}+\mathrm{Ni}^{+2} \rightarrow \mathrm{Fe}^{2+}+\mathrm{Ni} \\
& \mathrm{Zn}+\mathrm{Ni}^{2+} \rightarrow \mathrm{Zn}^{+2}+\mathrm{Ni}
\end{aligned}$
All these are spontaneous

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