First slide

Activity Series (OR) Electro chemicals series

Question

Identify the reaction from following having top position in EMF series (Std. red. potential) according to their electrode potential at 298 K.

Easy

A

$K^{+} + 1 e^{-} \to K_{(s)}$
B

${Mg}^{2 +} + 2 e^{-} \to {Mg}_{(s)}$
C

${Fe}^{2 +} + 2 e^{-} \to {Fe}_{(s)}$
D

${Au}^{3 +} + 3 e^{-} \to {Au}_{(s)}$

Solution

$\begin{array}{ll} {Au}^{3 +} + 3 e^{-} \to Au (s) E^{\circ} = 1 .40 V \\ {Fe}^{2 +} + 2 e^{-} \to Fe (s) E^{\circ} = - 0 .44 V \\ {Mg}^{2 +} + 2 e^{-} \to Mg (s) E^{\circ} = - 2 .36 V \\ K^{+} + 1 e^{-} \to K (s) E^{\circ} = - 2 .93 V \end{array}$
As per electrochemical series, ${Au}^{3 +}$ occupies the top position.

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