Why does the blue colour of copper sulphate solution fade when zinc is added?
Answer and explanation
Correct answer: The concentration of copper(II) ions in the solution decreases.
The blue colour of copper sulphate solution is due to copper(II) ions. Zinc is more reactive than copper, so it displaces copper from copper sulphate in a displacement reaction: \(\mathrm{Zn + CuSO_4 \rightarrow ZnSO_4 + Cu}\). The concentration of blue copper(II) ions decreases, so the blue colour fades. Sulphate ions remain in the solution and are not responsible for the colour change.
Frequently asked questions
What is the correct answer to this question?
The concentration of copper(II) ions in the solution decreases.
Why is this the correct answer?
The blue colour of copper sulphate solution is due to copper(II) ions. Zinc is more reactive than copper, so it displaces copper from copper sulphate in a displacement reaction: \(\mathrm{Zn + CuSO_4 \rightarrow ZnSO_4 + Cu}\). The concentration of blue copper(II) ions decreases, so the blue colour fades. Sulphate ions remain in the solution and are not responsible for the colour change.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
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