State three applications of a decomposition reaction.

(N/A) Applications of a decomposition reaction:
$(a)$ White silver chloride turns grey in sunlight due to the decomposition of silver chloride into silver and chlorine.
$2 AgCl (s) \xrightarrow{\text{sunlight}} 2 Ag (s) + Cl_2 (g)$
This reaction is used in black and white photography.
$(b)$ Potassium chlorate $(KClO_3)$ decomposes on heating to produce oxygen gas.
$2 KClO_3 (s) \xrightarrow{\text{heat}} 2 KCl (s) + 3 O_2 (g)$
This is a common laboratory method for the preparation of oxygen gas.
$(c)$ Quicklime $(CaO)$ is prepared by the thermal decomposition of calcium carbonate ($CaCO_3$,limestone).
$CaCO_3 (s) \xrightarrow{\text{heat}} CaO (s) + CO_2 (g)$
Quicklime is used in the manufacture of cement and for preparing slaked lime used in whitewashing.