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).