When Magnesium is burnt in air, awhile ash remain as left over. What is this?

Options

A. `MgO_(2)`
B. MgO
C. Mg
D. `Mg_(3)O`

Explanation

**Step-by-Step Solution:**

1. **Understanding the Reaction**: When magnesium is burnt in air, it reacts with oxygen present in the air. This is a combustion reaction, where a substance combines with oxygen to produce heat and light.

2. **Chemical Equation**: The chemical reaction can be represented by the following equation:
\[ 2 \text{Mg} + \text{O}_2 \rightarrow 2 \text{MgO} \]
Here, magnesium (Mg) reacts with oxygen (O₂) to form magnesium oxide (MgO).

3. **Formation of White Ash**: The product of this reaction, magnesium oxide (MgO), is a white solid that appears as ash after the combustion of magnesium. This is the "white ash" referred to in the question.

4. **Energy Release**: The combustion of magnesium is an exothermic reaction, meaning it releases energy in the form of heat and light. This is why burning magnesium produces a bright flame.

5. **Conclusion**: Therefore, the white ash that remains after burning magnesium in air is magnesium oxide (MgO).

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