Question

Why does the colour of copper sulphate change when an iron nail is kept in it? Justify your answer.

Answer 1

Blue colour of copper sulphate solution changes into green colour & then iron nail acquires a brownish look. This is because that iron is more reactive than copper.

$Fe+CuS{O}_4\to FeS{O}_4+Cu$
In this reaction, iron displaces copper from $CuS{O}_4$ solution.