From the following values for the half-cells:
(i) ; V
(ii) ; V
(iii) ; V
(iv) ; V
Which combination of two half-cells would result in a cell with largest potential?

Question

From the following $E^\circ$ values for the half-cells:
(i) $D \rightarrow D^{2+} + 2e^-$; $E^\circ = -1.5$ V
(ii) $B^+ + e^- \rightarrow B$; $E^\circ = -0.5$ V
(iii) $A^{3-} \rightarrow A^{2-} + e^-$; $E^\circ = 1.5$ V
(iv) $C^{2+} + e^- \rightarrow C^+$; $E^\circ = +0.5$ V
Which combination of two half-cells would result in a cell with largest potential?

Prashant Kotian · Accepted Answer

Correct answer: A. To maximize cell potential, we must couple the half-cell with the highest oxidation potential (anode) and the half-cell with the highest reduction potential (cathode). From (iii), oxidation has V. From (i), oxidation is -1.5 V, meaning its reduction is V. Combining the oxidation of A (iii) and the reduction of D (reverse of i) yields the maximum potential V. Therefore, correct answer is A.

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