Question

What is meant by reduction electrode potentials of zinc and copper being −0.76 V and + 0.34 V respectively? Can an aqueous solution of CuSO₄ be stored in a zinc vessel? Answer with reason.

Answer 1

The standard reduction potential of zinc is −0.76 V, which means that Zn²⁺ ions are less likely to be reduced (gain electrons) compared to hydrogen ions. Therefore, zinc metal is a strong reducing agent and readily loses electrons.

On the other hand, the standard reduction potential of copper is +0.34 V, indicating that Cu²⁺ ions are more likely to be reduced than hydrogen ions. Hence, copper is less reactive and is a weaker reducing agent than zinc.

Since zinc has a lower reduction potential than copper, it is more reactive. If an aqueous solution of CuSO₄ is stored in a zinc vessel, zinc will displace copper from the solution:

\[\ce{Zn_{(s)} + CuSO4_{(aq)} -> ZnSO4_{(aq)} + Cu_{(s)}}\]

This reaction is spontaneous, leading to corrosion of the zinc vessel and deposition of copper. Therefore, CuSO₄ solution cannot be stored in a zinc vessel.