Question

The statement that is not true about ozone is:

• A. It is a toxic gas and its reaction with $NO$ gives $N{O}_2$
• B. In the stratosphere, $CFCs$ release chlorine free radicals $\left(Cl\right)$ which reacts with $O_3$ to give chlorine dioxide radicals.
• C. In the atmosphere, it is depleted by $CFCs$.
• D. In the stratosphere, it forms a protective shield against $UV$ radiation.

Answer 1

The correct option is B In the stratosphere, $CFCs$ release chlorine free radicals $\left(Cl\right)$ which reacts with $O_3$ to give chlorine dioxide radicals.

Once CFCs are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. In stratosphere, they get broken down by powerful UV radiations, releasing chlorine free radical.

$C{F}_{2}C{l}_2\left(g\right)\stackrel{UV}{\to }\stackrel{\cdot }{C}l\left(g\right)+\stackrel{\cdot }{C}{F}_{2}Cl\left(g\right)$

The chlorine radical then react with stratospheric ozone to form chlorine monoxide radicals and molecular oxygen instead of chlorine dioxide radical.

$C{l}^{\cdot }\left(g\right)+O_3\left(g\right)\to Cl{O}^{\cdot }\left(g\right)+O_2\left(g\right)$

Hence, option (c) is not true about ozone.