A tarnished silver rod when kept in water containing magnesium bars regains its lustre. Justify.

Explanation

**Step-by-Step Solution:**

1. **Understanding Tarnishing**: Tarnishing of silver occurs when silver reacts with sulfur compounds in the air, forming silver sulfide (Ag2S), which gives the silver a dull appearance. This tarnished layer needs to be removed to restore the silver's luster.

2. **Setting the Scene**: In the given scenario, we have a tarnished silver rod that is placed in water containing magnesium bars. The presence of magnesium is crucial to the process.

3. **Reactivity of Metals**: Magnesium is a more reactive metal compared to silver. In the reactivity series of metals, magnesium is placed higher than silver, which means it can displace silver from its compounds.

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