Consider the following reduction processes:
a) Zn2+ + 2e- ⟶ Zn(s); E° = -0.76 V
b) Ca2+ + 2e- ⟶ Ca(s); E° = -2.87 V
c) Mg2+ + 2e- ⟶ Mg(s); E° = -2.36 V
d) Ni2+ + 2e-⟶ Ni(s); E° = -0.25 V
The reducing power of the metals increases in the order1
Zn < Mg < Ni < Ca
2
Ni < Zn < Mg < Ca
3
Ca < Zn < Mg < Ni
4
Ca < Mg < Zn < Ni