Chemistry

Problem

Under standard conditions, which of the following redox reactions would require an external power source to proceed as written? I.

\text{Cu}^{2+}+2\text{e}^- \rightarrow \text{Cu}(s)

E^\circ=+0.34\,\text{V}

II.

\text{Zn}^{2+}+2\text{e}^- \rightarrow \text{Zn}(s)

E^\circ=-0.76\,\text{V}

III.

2\text{H}^++2\text{e}^- \rightarrow \text{H}_2(g)

E^\circ=0.00\,\text{V}

IV.

\text{Ag}^++\text{e}^- \rightarrow \text{Ag}(s)

E^\circ=+0.80\,\text{V}

a) I only b) III only c) II only d) I and IV