A galvanic cell constructed from a half-cell and a half-cell produces 1.21 V when…

CHEMISTRY · Single correct · A Level · Chemistry · Electrode potentials · Electrode potentials

Problem

A galvanic cell constructed from a

\text{Mg}/\text{Mg}^{2+}

half-cell and a

\text{Sn}/\text{Sn}^{2+}

half-cell produces 1.21 V when operating spontaneously. A 2.00 V DC power supply is then connected so that its positive lead is attached to the tin electrode and its negative lead to the magnesium electrode. Once the power supply is turned on, which statement best describes the resulting processes? (a) The tin electrode becomes the anode where

\text{Sn}(s)

is oxidized to

\text{Sn}^{2+}

; the magnesium electrode becomes the cathode where

\text{Mg}^{2+}

is reduced to

\text{Mg}(s)

; electrons flow from tin through the power supply to magnesium. (b) Both electrodes act as anodes; magnesium and tin are simultaneously oxidized, and electrons flow from both electrodes into the power supply. (c) The tin electrode acts as the cathode where

\text{Sn}^{2+}

is reduced, the magnesium electrode acts as the anode where

\text{Mg}(s)

is oxidized, and electrons flow from magnesium through the power supply to tin. (d) Because the applied

2.00\text{ V}

is less than the cell’s standard potential

(E^\circ = 2.23\text{ V})

, the external source has no effect: current ceases and no further redox reaction occurs at either electrode.

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