When an iron nail is placed in copper sulphate solution, a reddish-brown coating forms on the nail and the solution turns green. What is the correct reason?
Answer and explanation
Correct answer: Iron, being more reactive than copper, displaces copper from copper sulphate to form iron sulphate.
Iron is above copper in the reactivity series, so it can displace copper from copper sulphate. The single-displacement equation is Fe + CuSO₄ → FeSO₄ + Cu. Copper separates and deposits as a reddish-brown coating on the nail, while aqueous iron(II) sulphate gives the solution a pale green colour. Therefore option A is correct. The observations prove that new substances form, so adsorption and the other reaction descriptions are unsuitable.
Frequently asked questions
What is the correct answer to this question?
Iron, being more reactive than copper, displaces copper from copper sulphate to form iron sulphate.
Why is this the correct answer?
Iron is above copper in the reactivity series, so it can displace copper from copper sulphate. The single-displacement equation is Fe + CuSO₄ → FeSO₄ + Cu. Copper separates and deposits as a reddish-brown coating on the nail, while aqueous iron(II) sulphate gives the solution a pale green colour. Therefore option A is correct. The observations prove that new substances form, so adsorption and the other reaction descriptions are unsuitable.
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.
