Question

Why does Mg and Zn2+ react? and why does Mg and Cu2+ react?

Answer 1

Between Mg and Zn, Mg is more electropositive. this is determined by the standard reduction potentials of the metals. the lower the reduction potential, the higher the metal has tendency to lose electrons:

Reduction potential of Mg = -2.38 V

Reduction potential of Zn = -0.76 V

From this, we see that Between Mg and Zn, Mg tends to be more electropositive. Hence the reaction:

Mg + Zn²⁺$\rightarrow$ Mg²⁺ + Zn

Proceeding like above,

Reduction potential of Mg = -2.38 V

Reduction potential of Cu = +0.16 V

Since Mg has more negative reduction potential, the reaction:

Mg + Cu²⁺$\rightarrow$ Mg²⁺ + Cu