Question

When a mixture of hydrogen and chlorine is exposed to sunlight, the greenish-yellow color of chlorine disappears. Give reason.

Answer 1

• When a mixture of hydrogen and chlorine is exposed to sunlight, the greenish-yellow color of chlorine disappears because the hydrogen and chlorine react in the presence of sunlight to produce Hydrogen Chloride gas.

$\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Chlorine}\mathrm{gas}}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}\stackrel{\mathrm{Sunlight}}{\to }\underset{\mathrm{Hydrogen}\mathrm{Chloride}}{2\mathrm{HCl}\left(\mathrm{g}\right)}+\mathrm{Energy}$

This is an exothermic reaction because the evolution of heat appears to be accelerated by moisture.