Question

The statement that is not true about ozone is:

Options

• In the stratosphere, CFCs release chlorine free radicals (Cl) which reacts with O₃ to give chlorine dioxide radicals.

• In the stratosphere, it forms as protective shield against UV radiation.

• It is a toxic gas and its reaction with NO gives NO₂.

• In the atmosphere, it is depleted by CFCs.

Answer 1

In the stratosphere, CFCs release chlorine free radicals (Cl) which reacts with O₃ to give chlorine dioxide radicals.

Explanation:

The upper stratosphere absorbs the UV radiation and decomposes to produce highly active chlorine free radicals which subsequently react with O₃ of the ozone layer to liberate oxygen and chlorine monoxide. Chlorine monoxide on further reaction with O₃ gives O₂ with active \[\ce{\overset{\bullet}{Cl}}\].

\[\ce{CFCl3(g) + hv -> CFCl2 {(free radical)} + \overset{\bullet}{Cl} {(active)}}\]

\[\ce{CF2Cl2(g) + hv -> CF2Cl {(free radical)} + \overset{\bullet}{Cl} {(active)}}\]

\[\ce{\overset{\bullet}{Cl} + O3 -> Cl\overset{\bullet}{O} + O2; Cl\overset{\bullet}{O} + O3 -> 2O2 + \overset{\bullet}{Cl} {(active)}}\]