Question

Which of the following metals should be chosen to react with $CuS{O}_4$ solution to make its colour change from blue to green?

• A. Iron (Fe)
• B. Copper (Cu)
• C. Gold (Au)
• D. Lead (Pb)

Answer 1

The correct option is A Iron (Fe)

$CuS{O}_4$ solution is blue in colour due to the presence of copper ion $C{u}^{2+}$. To see a colour change, Cu should be displaced from this solution.
We know that to displace a metal (in this case, copper $C{u}^{2+}$ from its salt solution $CuS{O}_4$), we need a metal which is more reactive than $Cu$.

Gold and lead are less reactive than copper and cannot displace it. Iron $Fe$ on the other hand is more reactive than $Cu$and hence can displace $Cu$ from its salt solution to form ferrous sulphate which is green in colour.