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The standard reduction potential 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 V , respectively.
The reaction $X+Y^{2+} \longrightarrow X^{2+}+Y$ will be spontaneous when
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The reaction $X+Y^{2+} \longrightarrow X^{2+}+Y$ will be spontaneous when
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Verified Answer
The correct answer is:
X=Zn, Y=Ni
The reaction is spontaneous when $\Delta G \lt 0$ and $E_{\text {cell }}^{\circ}\gt0 .$
$\begin{aligned} & \because \Delta G=-n F E^{\circ} \text { and } E^{\circ}\gt0 \\ & \text { Also } E_{\text {cell }}^{\circ}=E_{\text {oxi }}^{\circ}+E_{\text {red }}^{\circ} \text { (or) } E_{\text {cathode }}^{\circ}-E_{\text {anode }}^{\circ}\end{aligned}$
Here,
Thus, $E_{\text {cell }}^{\circ}$ for
(a) -0.21 V , i.e. $E_{\text {cell }}^0 \lt 0$
(b) -0.53 V , i.e. $E_{\text {cell }}^0 \lt 0$
(c) -0.32 V , i.e. $E_{\text {cell }}^{\circ} \lt 0$
(d) 0.53 V , i.e. $E^{\circ}\gt0$
$\begin{aligned} & \because \Delta G=-n F E^{\circ} \text { and } E^{\circ}\gt0 \\ & \text { Also } E_{\text {cell }}^{\circ}=E_{\text {oxi }}^{\circ}+E_{\text {red }}^{\circ} \text { (or) } E_{\text {cathode }}^{\circ}-E_{\text {anode }}^{\circ}\end{aligned}$
Here,
Thus, $E_{\text {cell }}^{\circ}$ for
(a) -0.21 V , i.e. $E_{\text {cell }}^0 \lt 0$
(b) -0.53 V , i.e. $E_{\text {cell }}^0 \lt 0$
(c) -0.32 V , i.e. $E_{\text {cell }}^{\circ} \lt 0$
(d) 0.53 V , i.e. $E^{\circ}\gt0$
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