State the reason for the following behaviour of zinc metal:
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.

Explanation

### Step-by-Step Solution:

1. **Understanding the Metal Activity Series**:
The metal activity series is a list that ranks metals based on their reactivity. The more reactive a metal is, the more likely it is to displace another metal from its compound in solution.

2. **Analyzing the Reaction with Mercuric Chloride**:
When zinc metal is placed in a solution of mercuric chloride (HgCl₂), a reaction occurs because zinc is more reactive than mercury. The reaction can be represented as:
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