When magnesium is burnt in air, the weight of white ash obtained is more than magnesium metal.

Explanation

### Step-by-Step Solution:

1. **Understanding the Reaction**: When magnesium (Mg) is burned in air, it reacts with oxygen (O₂) present in the air. This reaction produces magnesium oxide (MgO), which is a white ash.

2. **Chemical Equation**: The chemical reaction can be represented by the equation:
\[ 2 \text{Mg} + \text{O}_2 \rightarrow 2 \text{MgO} \]
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