Question

Give an example of a reaction that requires light.

Answer 1

Photodecomposition reaction:

1. It takes place in the presence of light.
2. In this type of reaction, the reactants absorb light and are broken down into their constituents elements.

Decomposition of Silver chloride:-

1. When silver chloride$\left(\mathrm{AgCl}\right)$ is kept in presence of sunlight, the silver chloride compound absorbs the light.
2. By absorbing this light it decomposes to form silver and chloride gas.
3. The reaction is:

$\underset{\mathrm{Silver}\mathrm{chloride}}{2\mathrm{AgCl}\left(\mathrm{s}\right)}\stackrel{\mathrm{light}}{\to }\underset{\mathrm{Silver}}{2\mathrm{Ag}\left(\mathrm{s}\right)}+\underset{\mathrm{Chlorine}\mathrm{gas}}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}$

Therefore, an example of a reaction that requires light is the decomposition of silver chloride $\left(\mathrm{AgCl}\right)$ in presence of light:

$\underset{\mathrm{Silver}\mathrm{chloride}}{2\mathrm{AgCl}\left(\mathrm{s}\right)}\stackrel{\mathrm{light}}{\to }\underset{\mathrm{Silver}}{2\mathrm{Ag}\left(\mathrm{s}\right)}+\underset{\mathrm{Chlorine}\mathrm{gas}}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}$