Question

What is the chemical composition of acid rain?

Answer 1

Hint: Acid rain is caused due to various gases that are already present in the air. These gases are released into air by industries and factories. The phenomenon of acid rain was rare in the early times. But in the recent decades it has become quite frequent.

Complete answer:
In simple words we can say that rain which involves acid in it is acid rain. These acids are Sulphuric acid, carbonic acid and nitric acid that form the constituents of the acid rain. Hence, the pH of acid rain ranges between $4.2$ to $4.4$.
These acids are formed when gases such as Sulphur dioxide, carbon-di-oxide and nitrogen oxide mix with rain water and the atmospheric oxygen to cause acid rain. These particles are released when hydrocarbons such as coal, crude oil or gasoline are burnt in the factories.
The two major components of acid rain are Sulphuric acid and nitric acid. Let’s see how these acids are prepared in the air from rainwater.
First we’ll see the preparation of Sulphuric acid from Sulphur dioxide. Humans add it to the atmosphere by burning fossil fuels and naturally it comes from volcanic eruptions.
1. Sulphur dioxide reacts with OH. radical and oxygen to form, Hydroperoxyl radical and Sulphur trioxide.

$SO_2 + OH + O_2 \to SO_3 +HO_2$
This sulphur trioxide reacts with water to form Sulphuric acid.

$SO_3 + H_2O \to H_2SO_4$
2. Now, nitric acid is prepared by the reaction between nitrogen oxide and –OH obtained from water. It is added naturally by lightning and humans increase its amount in the atmosphere by combustion of gasoline.

$NO_2 + OH \to HNO_3$
3. Lastly carbonic acid is formed by carbon-di-oxide and water. It is mainly made by the natural decomposition of dead animals and plants.

$CO_2 + H_2O \to H_2CO_3$
These three acids are produced in acid rain.

Note:
Acid rain affects humans as it lowers the pH of the soil. It affects the growth of vegetables, and fruits. Consuming such things will affect the overall growth of humans and make them sick, too. Acid rain also corrodes the monuments made up of marble and limestone.