Question

A student adds lead and silver to two different test tubes containing an equal amount of copper sulphate solution. The student observes that the colour of the solution in the test tube with lead changes. What explains the change in the colour of the solution?

(a) A displacement reaction takes place as lead displaces copper from the solution.

(b) A combination reaction takes place as lead combines with sulphate in the solution.

(c) A double displacement reaction takes place as silver combines with sulphate in the solution.

(d) A decomposition reaction takes place as copper dissociates from sulphate in the solution.​

Answer 1

A student adds lead and silver to two different test tubes containing an equal amount of copper sulphate solution. The student observes that the colour of the solution in the test tube with lead changes. What explains the change in the colour of the solution?

(a) A displacement reaction takes place as lead displaces copper from the solution.

Answer 2

The change in colour of the solution is explained by the fact that A displacement reaction takes place as lead displaces copper from the solution.

• A high reduction potential indicates a higher tendency of the element to get reduced than to get oxidised.

• Upon observing the standard reduction potential of Copper, Silver and Lead we observe that Silver(Ag) has highest positive reduction potential followed by Copper (Cu) and Lead(Pb) which has a negative reduction potential.
• So, when Ag is added to a solution of CuSO₄, it is unable to displace Cu.
• Conversely, when Pb is added to a solution of CuSO₄, it displaces Cu to form PbSO₄ and Cu is deposited in its free state, leading to a change in the colour of the solution.

Hence option (A) A displacement reaction takes place as lead displaces copper from the solution is the correct answer.