Question

why does the colour of copper sulphate solution change when an iron nail is dipped in it ​

Answer 1

Explanation:

When an iron nail immersed in the solution of copper sulphate than iron displaces copper from the solution of copper sulphate because iron is more reactive than copper. Therefore copper sulphate solution colour changes from blue to pale green.

Reaction

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

In this reaction following two processes take place:

• Cu²⁺ + 2e = Cu⁰ (re­duc­tion process, Cu²⁺ is the ox­i­dizing agent)
• Fe⁰ – 2e = Fe²⁺ (ox­i­da­tion process, Fe⁰ is the re­duc­ing agent)

The reaction can be double displacement reaction as well as redox reaction (oxidation and reduction both takes place simultaneously).

Answer 2

when an iron nail is dipped in copper sulphate solutions change into iron sulphate solutions and colour change from blue to green