Question

The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is:

• A. Blue
• B. Pale green
• C. Yellow
• D. Reddish brown

Hint:

In displacement reactions, a more reactive metal (iron) displaces a less reactive metal (copper) from its solution. This results in the formation of solid copper and a colour change.

Answer 1

The Correct Option is D

Iron nails undergo a displacement reaction when immersed in a copper sulphate solution. Iron (Fe) replaces copper (Cu) in copper sulphate \((CuSO_4)\) because iron is more reactive. The reaction is:\[\text{Fe} (s) + \text{CuSO}_4 (aq) \rightarrow \text{FeSO}_4 (aq) + \text{Cu} (s)\]Copper metal is released from the solution and appears as a reddish-brown solid at the container's base, while iron(II) sulphate forms in solution. The color change is due to the formation of reddish-brown copper metal. Therefore, the correct answer is (D) Reddish brown.