Write true or false for the following statement:
The thermal decomposition reaction of calcium sulphate (gypsum) is used in black and white photography.

State three applications of a decomposition reaction.

$(a)$ Give an example of a combination reaction which is exothermic.
$(b)$ Identify the oxidizing agent and reducing agent in the following reaction:
$H_{2}S + Cl_{2} \rightarrow 2HCl + S$
$(c)$ Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in the open. Suggest one method to prevent it.

What happens when a piece of $(i)$ Silver metal is added to copper sulphate solution? Also,write the balanced chemical equation if the reaction occurs.

Give differences between the displacement and double displacement reactions.

Complete the following reaction:
$2 FeSO_{4} \xrightarrow{\text{Heat}} Fe_{2}O_{3} + \dots + \dots$