On placing a piece of zinc metal in a solution of mercuric chloride, it acquires a shining silvery surface but when it is placed in a solution of magnesium sulphate, no change is observed. Explain.

Explanation

Zinc is more reactive than mercury. Herice, it displaces mercury from mercuric chloride solution. This mercury deposits on the zinc metal. Hence, it acquires a shining silvery surface
`underset("Zinc")(Zn)+ underset("chloride")underset("Mercuric")(HgCl_2) rarr underset("chloride")underset("Zinc")(ZnCl_2)+ underset("Mercury")(Hg)`
No change is observed when zinc metal is placed in magnesium sulphate solution. This is because zinc is less reactive than magnesium. Hence, zinc cannot displace magnesium from magnesium sulphate solution.