Question:
The standard reduction potential for Zn\(^{2+}\)/Zn, Ni\(^{2+}\)/Ni and Fe\(^{2+}\)/Fe are -0.76, -0.23 and -0.44 V respectively. The reaction X + Y\(^{2+}\) \( \rightarrow \) X\(^{2+}\) + Y will have more negative \( \Delta G \) value when X and Y are
The standard reduction potential for Zn\(^{2+}\)/Zn, Ni\(^{2+}\)/Ni and Fe\(^{2+}\)/Fe are -0.76, -0.23 and -0.44 V respectively. The reaction X + Y\(^{2+}\) \( \rightarrow \) X\(^{2+}\) + Y will have more negative \( \Delta G \) value when X and Y are
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Lower E° = better reducing agent, higher E° = better oxidizing agent.
Updated On: May 2, 2026
- X = Ni; Y = Fe
- X = Ni; Y = Zn
- X = Fe; Y = Zn
- X = Zn; Y = Ni
- X = Fe; Y = Ni
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The Correct Option is D
Solution and Explanation
Concept: Relation between $\Delta G$ and EMF
\[ \Delta G = -nFE^\circ_{\text{cell}} \]
• More positive $E^\circ$ ⇒ more negative $\Delta G$ ---
Step 1: Given reduction potentials
\[ Zn = -0.76,\quad Fe = -0.44,\quad Ni = -0.23 \] ---
Step 2: Choose strongest oxidizing agent
Higher value ⇒ stronger reduction tendency \[ Ni^{2+} > Fe^{2+} > Zn^{2+} \] ---
Step 3: Best combination
We need:
• X = strongest reducing agent (lowest E°)
• Y = strongest oxidizing agent (highest E°) \[ X = Zn,\quad Y = Ni \] ---
Step 4: Maximum EMF
\[ E^\circ = (-0.23) - (-0.76) = +0.53 \text{ V} \] Maximum positive ⇒ most negative $\Delta G$ --- Final Answer: \[ \boxed{\text{(D)}} \]
\[ \Delta G = -nFE^\circ_{\text{cell}} \]
• More positive $E^\circ$ ⇒ more negative $\Delta G$ ---
Step 1: Given reduction potentials
\[ Zn = -0.76,\quad Fe = -0.44,\quad Ni = -0.23 \] ---
Step 2: Choose strongest oxidizing agent
Higher value ⇒ stronger reduction tendency \[ Ni^{2+} > Fe^{2+} > Zn^{2+} \] ---
Step 3: Best combination
We need:
• X = strongest reducing agent (lowest E°)
• Y = strongest oxidizing agent (highest E°) \[ X = Zn,\quad Y = Ni \] ---
Step 4: Maximum EMF
\[ E^\circ = (-0.23) - (-0.76) = +0.53 \text{ V} \] Maximum positive ⇒ most negative $\Delta G$ --- Final Answer: \[ \boxed{\text{(D)}} \]
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