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

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

Official previous-year question

Verified 1 Aug 2026.

Options

ANew Substance in Solution : Iron Sulphate
BInitial Solution Colour : Green
CBrown Deposit : Iron Sulphate
DFinal Solution Colour : Blue

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Solution

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).

Your note

More from Chapter 2: Physical and chemical changes

With reference to the burning of a magnesium ribbon, consider the following statements: 1. It burns with a dull blue flame. 2. The ash formed is chemically different from the magnesium ribbon. 3. The reaction produces a new substance called magnesium oxide. Which of the statements given above is/are correct?

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When the ash obtained from burning magnesium is dissolved in water, the resulting solution is:

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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?

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With reference to the "Lime Water Test", consider the following statements: 1. It is a standard test for Carbon Dioxide gas. 2. The milky appearance is due to the formation of Calcium Oxide. 3. The chemical name of lime water is Calcium Hydroxide. Which of the statements given above is/are correct?

medium

Which of the following is NOT a characteristic indicator that a chemical change has taken place?

easy

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The correct option is

New Substance in Solution : Iron Sulphate

Explanation

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.