Question

Which of the following statements are correct?

• A. is a toxic pollutant that causes acid rain
• B. is very soluble in water and undergoes complete ionization
• C. is a lewis acid
• D. is an anti-chlor, disinfectant and a preservative

Answer 1

Answer: (A), (C), (D)

The correct options are
A is a toxic pollutant that causes acid rain
C is a lewis acid
D is an anti-chlor, disinfectant and a preservative

It is common knowledge that $S{O}_2$ is a toxic pollutant. When it reaches the upper atmosphere $S{O}_2$ is oxidized by OH – the hydroxyl radical and hydrated to produce droplets of sulphuric acid. You will encounter some unheard of reactants or products in the following 3 reactions, which together explain a simple mechanism for acid rain.
$OH+S{O}_2\to HOS{O}_2$
$O_2+HOS{O}_2\to S{O}_3+H{O}_2$
$S{O}_3+H_{2}O\to H_{2}S{O}_4$
The product of the third reaction precipitates as “acid rain” and this rain could happen anywhere – far removed from the source of pollution. This is why $S{O}_2$ pollution should be mitigated
With S atom as the acceptor site, $S{O}_2$ acts as a lewis acid. Do note that in some cases, because of the lone pair on S atom, it can also act as a lewis base!
$S{O}_2$ though very soluble in water, does not ionize fully or to a great extent. Like $C{O}_2$ or $N{H}_3$ , even after dissolving, it exists as $S{O}_2$ molecule only! Only a tiny proportion forms sulphurous acid,
$S{O}_2\left(g\right)+H_{2}O\left(l\right)\rightleftharpoons H_{2}S{O}_3\left(aq\right)$
Uses of $S{O}_2$:
1. It is used to produce $S{O}_3$ for the manufacture of Sulphuric acid (contact process)
2. $S{O}_2$ is used to bleach silk or wool
3. In its liquid form, $S{O}_2$ is an important solvent for organic and inorganic chemicals
4. Also, Sulphur dioxide is an important chemical used for refining petroleum and sugar
5. $S{O}_2$ gas is an important ingredient to produce industrial chemicals like Sodium and Calcium Hydrogen Sulphites