E deg(Au^3+/Au) = 1.50 V and E deg(Au+/Au) = 1.68 V. The standard potential of the couple Au^3+/Au+ (Au^3+ + 2e- -> Au+) is

JEE Main levelSingle correct optionDifficulty 2 of 3ec074

$E^{\circ} (Au X^{3 +} / Au) = 1.50 V$ and $E^{\circ} (Au X^{+} / Au) = 1.68 V$ . The standard potential of the couple $Au X^{3 +} / Au X^{+}$ ( $Au X^{3 +} + 2 e X^{-} Au X^{+}$ ) is

Δ G^{\circ} (Au X^{3 +} Au) = Δ G^{\circ} (Au X^{3 +} Au X^{+}) + Δ G^{\circ} (Au X^{+} Au)

- 3 F (1.50) = - 2 F E^{\circ} - F (1.68)

. So

E^{\circ} = \frac{3 ( 1.50 ) - 1.68}{2} = \frac{4.50 - 1.68}{2} = 1.41 V

. Option B is the direct difference and option C the simple average; neither accounts for the electron numbers.