Why does the Colour of Copper Sulphate Change When an Iron Nail is Added to it? Justify your Answer

Answer:

When Iron nail is dropped in the solution of copper sulphate, the iron displaces the copper from the solution of copper as iron is a strong displacement agent than copper. 

The chemical reaction taking place is:

CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)

In this response following two cycles happen:

Cu²⁺ + 2e– → Cu⁰ (reduction, Cu²⁺ being the oxidizing agent)

Fe⁰ – 2e– → Fe²⁺ (oxidation, Fe⁰ being the reducing agent)

The reaction occurring can be either of the two, redox or double displacement reaction.

Copper forms a layer on the Iron surface, making the solution turn green from blue. Ferrous sulphate is formed from copper sulphate.