With reference to the reaction between Copper Sulphate and Iron, consider the following statements: 1. The colour of the solution changes from blue to green. 2. The green colour is due to the formation of Copper Oxide. 3. A brown deposit forms on the iron object, which is Rust (Iron Oxide). Which of the statements given above is/are correct?

The correct option is (a). Explanation The reaction between iron and copper sulphate is a classic example of a single displacement reaction. This reaction is governed by the reactivity series of metals, where a more reactive metal displaces a less reactive metal from its salt solution. Statement-wise Analysis: - Statement 1 is Correct: Copper sulphate solution ($CuSO_4$) is characteristically blue. When iron is immersed in it, iron displaces copper to form ferrous sulphate ($FeSO_4$), which is light green in colour. Consequently, the solution fades from blue to green. - Statement 2 is Incorrect: The green colour observed in the solution is attributed to the formation of Ferrous Sulphate ($FeSO_4$). Copper Oxide ($CuO$) is typically black and is not a product of this displacement reaction. - Statement 3 is Incorrect: The reddish-brown deposit found on the iron object is pure Copper metal ($Cu$) that has been displaced from the solution. Rust is hydrated iron oxide ($Fe_2O_3 \cdot xH_2O$), which forms through the oxidation of iron by atmospheric oxygen and moisture, distinct from this chemical displacement. Key Takeaway: Iron is more reactive than copper; therefore, it displaces copper from copper sulphate solution, resulting in the formation of green ferrous sulphate and the deposition of reddish-brown copper metal.

With reference to the reaction between Copper Sulp... - NCERT Class 7 Science MCQ

Solution

The correct option is (a).

Explanation

The reaction between iron and copper sulphate is a classic example of a single displacement reaction. This reaction is governed by the reactivity series of metals, where a more reactive metal displaces a less reactive metal from its salt solution.

Statement-wise Analysis:

Statement 1 is Correct: Copper sulphate solution ($CuSO_4$) is characteristically blue. When iron is immersed in it, iron displaces copper to form ferrous sulphate ($FeSO_4$), which is light green in colour. Consequently, the solution fades from blue to green.
Statement 2 is Incorrect: The green colour observed in the solution is attributed to the formation of Ferrous Sulphate ($FeSO_4$). Copper Oxide ($CuO$) is typically black and is not a product of this displacement reaction.
Statement 3 is Incorrect: The reddish-brown deposit found on the iron object is pure Copper metal ($Cu$) that has been displaced from the solution. Rust is hydrated iron oxide ($Fe_2O_3 \cdot xH_2O$), which forms through the oxidation of iron by atmospheric oxygen and moisture, distinct from this chemical displacement.

Key Takeaway: Iron is more reactive than copper; therefore, it displaces copper from copper sulphate solution, resulting in the formation of green ferrous sulphate and the deposition of reddish-brown copper metal.

NCERT Class 7 Science — Chapter 2: Physical and chemical changes

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