What happens when
(i) Magnesium is burnt in air
(ii) Quicklime is heated with silica
(iii) Calcium nitrate is heated
(iv) Chlorine reacts with slaked lime

Explanation

Let's break down the reactions step by step:

### (i) Magnesium is burnt in air
1. **Identify the reactants**: Magnesium (Mg) and air (which contains oxygen, O2).
2. **Write the reaction**: When magnesium burns in air, it primarily reacts with oxygen to form magnesium oxide (MgO).
\[ 2Mg + O_2 \rightarrow 2MgO \]
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