A solution of a substance `X` is used for whitewashing.
(i) Name the substance `X` and write its formula.
(ii) Write the reaction of the substance `X` named in (i) above with water.

Answer

### Step-by-Step Solution:

**(i)** The substance `X` used for whitewashing is **calcium oxide**. The chemical formula for calcium oxide is:
\[ \text{X} = \text{Calcium Oxide (CaO)} \]

**(ii)** When calcium oxide reacts with water, it undergoes a reaction to form calcium hydroxide. The balanced chemical equation for this reaction is:
\[ \text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 \]

### Summary of the Solution:
1. The substance `X` is calcium oxide (CaO).
2. The reaction of calcium oxide with water is:
\[ \text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 \]