Question

An iron knife dropped in a blue copper sulphate solution turns the solution light green

Answer 1

The metal iron(Fe) is more reactive than Copper,

So, when iron knife is dipped in Copper sulphate solution (CuSO4·5H2O),

Iron being more reactive than copper displaces it from its salt soution forming iron (ll) Sulphate (FeSo4.7H2O) which is green in colour.

Thanks!!!