Is it essential that oxidation and reduction must occur side by side in a chemical reaction? Explain.

In a chemical reaction, if one substance is oxidized, the other substance must necessarily be reduced. This is because the electrons lost during oxidation are simultaneously gained during reduction and vice versa.

For example, Zinc reacts with copper sulphate to form zinc sulphate and copper.

CuSO₄ + Zn ⟶ ZnSO₄ + Cu

Cu²⁺ SO₄^2- + Zn ⟶ Zn²⁺ SO₄^2- + Cu

Writing half-reaction,

Zn ⟶ Zn²⁺ + 2e^- (Oxidation)

Cu²⁺ + 2e^- ⟶ Cu (Reduction)

They occur simultaneously as

Cu²⁺ + Zn ⟶ Zn²⁺ + Cu

Thus, oxidation and reduction always occur simultaneously in a chemical reaction.