Which of the following pairs is correctly matched regarding the reaction of Copper Sulphate with Iron?

The correct option is

New Substance in Solution : Iron Sulphate

Explanation

The reaction between iron and copper sulphate is a classic example of a single displacement reaction governed by the reactivity series of metals. In this reaction, iron, being more reactive than copper, displaces copper from its salt solution.

The chemical equation for this reaction is:

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

Option-wise Analysis

• Option (a) is Incorrect: The initial solution is Copper Sulphate (CuSO₄), which is distinctively blue in colour, not green.
• Option (b) is Incorrect: As the reaction proceeds, the blue colour fades and changes to light green. This colour change indicates the formation of Ferrous Sulphate (FeSO₄).
• Option (c) is Incorrect: The reddish-brown deposit found on the iron nail (or iron object) is Copper metal (Cu), which precipitates out of the solution. Iron Sulphate remains dissolved in the aqueous solution.
• Option (d) is Correct: The new substance formed in the solution is indeed Iron Sulphate (FeSO₄), which is responsible for the green colour of the final solution.

Key Takeaway: In a displacement reaction, a more reactive metal (Iron) displaces a less reactive metal (Copper) from its aqueous salt solution, resulting in a colour change from blue (Copper Sulphate) to light green (Iron Sulphate).