Standard electrode potentials for a few half cells are mentioned below : aligned & E_ Cu^ 2+ / Cu ^ =0.34 ~V, E_ Zn^ 2+ / Zn ^ =-0.76 ~V & E_ Ag^ + / Ag ^ =0.80 ~V, E_ Mg^ 2+ / Mg ^ =-2.37 ~V aligned Which one of the

Correct answer: A. Zn|Zn^ 2+ (1 M)||Ag^ + (1 M)| Ag gathered Δ G^ =-nFE^ Option (1) E^ =0.8+0.76 =1.56 V Δ G^ =-2 × F × 1.56 =-3.12 V Option (2) E^ =-2.37+0.76 =-1.61 V Δ G^ =-2 × F ×(-1.61) =+3.22 V Option (3) E^ =-2.37-0.8 =-3.17 V . array c Δ G^ =-2 array ) × F ×(-3.17) =+6.34 Option (4) E^ =0.8-0.34 =0.46 V Δ G^ =-2 × F × 0.46 =-0.92 V gathered

JEE Main 202523 JanuaryEvening Shift

Exam: JEE Main
Year: 2025
Date: 23 January
Shift: Evening Shift
Subject: Chemistry
Chapter: Electrochemistry

JEE Main 2025 · 23 January · Evening Shift · Chemistry · Electrochemistry

Standard electrode potentials for a few half cells are mentioned...

Standard electrode potentials for a few half cells are mentioned below :

\begin{aligned} & \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{~V}, \mathrm{E}_{\mathrm{Zn}^{2+} / \mathrm{Zn}}^{\circ}=-0.76 \mathrm{~V} \\ & \mathrm{E}_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.80 \mathrm{~V}, \mathrm{E}_{\mathrm{Mg}^{2+} / \mathrm{Mg}}^{\circ}=-2.37 \mathrm{~V} \end{aligned}

Which one of the following cells gives the most negative value of

\Delta \mathrm{G}^{\circ}

Options

A $\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 \mathrm{M})\right|\left|\mathrm{Ag}^{+}(1 \mathrm{M})\right| \mathrm{Ag}$
B $\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 \mathrm{M})\right|\left|\mathrm{Mg}^{2+}(1 \mathrm{M})\right| \mathrm{Mg}$
C $\mathrm{Ag}\left|\mathrm{Ag}^{+}(1 \mathrm{M})\right|\left|\mathrm{Mg}^{2+}(1 \mathrm{M})\right| \mathrm{Mg}$
D $\mathrm{Cu}\left|\mathrm{Cu}^{2+}(1 \mathrm{M}) \| \mathrm{Ag}^{+}(1 \mathrm{M})\right| \mathrm{Ag}$

Correct answer

A. $\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 \mathrm{M})\right|\left|\mathrm{Ag}^{+}(1 \mathrm{M})\right| \mathrm{Ag}$

Step-by-step solution

\begin{gathered}\because \Delta \mathrm{G}^{\circ}=-\mathrm{nFE}^{\circ} \\ \text{ Option }(1) \mathrm{E}^{\circ}=0.8+0.76 \\ =1.56 \mathrm{ V} \\ \therefore \Delta \mathrm{G}^{\circ}=-2 \times \mathrm{F} \times 1.56 \\ =-3.12 \mathrm{ V} \\ \text{ Option (2) } \mathrm{E}^{\circ}=-2.37+0.76 \\ =-1.61 \mathrm{ V} \\ \therefore \Delta \mathrm{G}^{\circ}=-2 \times \mathrm{F} \times(-1.61) \\ =+3.22 \mathrm{ V} \\ \text{ Option (3) } \mathrm{E}^{\circ}=-2.37-0.8 \\ =-3.17 \mathrm{ V} \\ \left.

\begin{array}{c}\Delta \mathrm{G}^{\circ}=-2\end{array}

\right) \times \mathrm{F} \times(-3.17) \\ =+6.34 \\ \text{ Option }(4) \mathrm{E}^{\circ}=0.8-0.34 \\ =0.46 \mathrm{ V} \\ \Delta \mathrm{G}^{\circ}=-2 \times \mathrm{F} \times 0.46 \\ =-0.92 \mathrm{ V}\end{gathered}

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