Question

Reactions which take place in the presence of light are known as ____________.

Answer 1

Photochemical reactions:

• Some reactions take place only when the reactants are exposed to light.
• Such reactions are called photochemical reactions.
• For example hydrogen($\mathrm{H}$) reacts with chlorine($\mathrm{Cl}$) in the presence of sunlight resulting in the formation of hydrochloric acid
• $\mathrm{H}2+{\mathrm{Cl}}_2\stackrel{\mathrm{Diffused}\mathrm{sunlight}}{\to }2\mathrm{HCl}$.

Therefore,Reactions which take place in the presence of light are known as photochemical reactions