(a) List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable example.

Heat, light, electricity

\[2 \mathrm{AgBr}(\mathrm{~s}) \xrightarrow{\text { Sunlight }} 2 \mathrm{Ag}(\mathrm{~s})+\mathrm{Br}_{2}(\mathrm{~g}) \]

Observation:

Water droplets on upper part of the test tube/Colour changes from green to white/White to brown on heating strongly/Pungent smell of burning Sulphur.

\[\begin{aligned} & \mathrm{Fe} \mathrm{SO}_{4.7 \mathrm{H}_{2} \mathrm{O}} \rightarrow \mathrm{FeSO}_{4}+7 \mathrm{H}_{2} \mathrm{O} \\ & 2 \mathrm{FeSO}_{4} \xrightarrow{\text { Heat }} \mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{SO}_{3}+\mathrm{SO}_{2} \end{aligned} \]