Question

blue colour of copper sulphate is changed when iron filings are added to it . why ?

Answer 1

when an iron nail is placed in a copper sulphate solution solution, iron displaces copper from copper sulphate solution forming iron sulphate, which is light green in colour. It is because iron is more reactive than copper.

Answer 2

Because iron is more reactive than copper, when an iron nail is placed in a copper sulphate solution, the iron displaces the copper from the solution. As a result, the copper sulphate solution turns a light green color.

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

Two steps happen in this reaction:

Cu²⁺ + 2e = Cu⁰ (ox­i­dizing agent Cu2+)

Fe⁰ – 2e = Fe²⁺ (reduction process, Fe0 is the reduc­ing agent)

Double displacement reactions and redox reactions are also possible (oxidation and reduction both takes place simultaneously).

Explanation :

• When an iron nail is dipped in copper sulphate solution, a brown copper coating forms on the surface of the iron, and the copper sulphate solution changes color from blue to pale green.
• Because it displaces copper from the copper sulphate solution, the reaction reveals that iron is more reactive than copper.