An unknown inorganic compound (X) loses it water of crystallisation on heating and its aqueous solution gives the following reaction.
(i) It gives a white turbidity with dilute hydrochloric acid solution.
(ii) It decolourises a solution of iodine in potassium iodide.
(iii) It gives a white precipitate with silver nitrate solution which turns black on standing. Identify the compound (X) and give chemical equations for the reaction at step (i) to (iii).

Explanation

To identify the unknown inorganic compound (X) and provide the chemical equations for the reactions described, we can follow these steps:

### Step 1: Identify the Compound (X)
The unknown compound (X) loses its water of crystallization upon heating. Given the reactions it undergoes, we can deduce that it is likely sodium thiosulphate (Na2S2O3·5H2O), which is known to decompose and exhibit the behaviors described in the reactions.

### Step 2: Reaction with Dilute Hydrochloric Acid
When sodium thiosulphate is treated with dilute hydrochloric acid (HCl), it produces sodium chloride (NaCl), sulfur dioxide (SO2), sulfur (S), and water (H2O). The sulfur produced is responsible for the white turbidity observed.

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