Question

What happens when a piece of

(i) zinc metal is added to copper sulphate solution?

(ii) aluminium metal is added to dilute hydrochloric acid?

(iii) silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs.

Answer 1

(i) When zinc metal is added to a solution of copper sulphate (CuSO₄​), the blue colour of the latter changes to colourless as zinc sulphate (ZnSO₄​) is formed. In this displacement reaction, zinc being more active metal than copper displaces it to form zinc sulphate, as shown below:

Zn(s) + CuSO₄​(aq) → ZnSO₄​(aq) + Cu(s)
                 (blue)               (colourless)

(ii) Hydrogen gas is evolved.

Reason Zinc reacts with copper sulphate to form colourless zinc sulphate solution and solid copper in deposited form.

(iii) No reaction occurs.

Reason Silver metal is less reactive than copper, therefore, it cannot displace copper from copper sulphate solution.

Ag(s) + CuSO₄(aq) → No reaction

Silver     Copper sulphate