1.
Consider the following reduction processes:

Zn2+ (aq)+2e−→Zn (s)\text{Zn}^{2+}\,(\text{aq}) + 2e^- \rightarrow \text{Zn}\,(\text{s}); E∘=−0.76 VE^\circ = -0.76\,\text{V}

Ca2+ (aq)+2e−→Ca (s)\text{Ca}^{2+}\,(\text{aq}) + 2e^- \rightarrow \text{Ca}\,(\text{s}); E∘=−2.87 VE^\circ = -2.87\,\text{V}

Mg2+ (aq)+2e−→Mg (s)\text{Mg}^{2+}\,(\text{aq}) + 2e^- \rightarrow \text{Mg}\,(\text{s}); E∘=−2.36 VE^\circ = -2.36\,\text{V}

Ni2+ (aq)+2e−→Ni (s)\text{Ni}^{2+}\,(\text{aq}) + 2e^- \rightarrow \text{Ni}\,(\text{s}); E∘=−0.25 VE^\circ = -0.25\,\text{V}

The reducing power of the metals increases in the order: