Why does the blue colour of copper sulphate solution fade and turn green when an iron nail is added?
Answer and explanation
Correct answer: Iron displaces copper from copper sulphate and forms iron sulphate.
Iron is more reactive than copper, so it displaces copper from copper sulphate solution. In this displacement reaction, pale-green iron sulphate forms and copper is deposited as a reddish-brown coating on the nail: \(\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\). Therefore, the blue solution fades and appears green. Option B is incorrect because copper is less reactive than iron and cannot displace iron.
Frequently asked questions
What is the correct answer to this question?
Iron displaces copper from copper sulphate and forms iron sulphate.
Why is this the correct answer?
Iron is more reactive than copper, so it displaces copper from copper sulphate solution. In this displacement reaction, pale-green iron sulphate forms and copper is deposited as a reddish-brown coating on the nail: \(\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\). Therefore, the blue solution fades and appears green. Option B is incorrect because copper is less reactive than iron and cannot displace iron.
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.
