Question

Define photochemical reactions.

Answer 1

The reactions which take place only when the reactants are exposed to light are known as photochemical reactions.

Let us take an example-

$\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2}+\underset{\mathrm{Chlorine}}{{\mathrm{Cl}}_2}\stackrel{Diffusedsunlight}{\to }\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}}$

In the above reaction, Hydrogen and Chlorine are reacting in presence of diffused sunlight to give us Hydrochloric acid.

The reaction is using light.

Thus, it is an example of a photochemical reaction.