Question

Acid rain is caused due to which gas?
a. $N{O_3}$
b. $S{O_2}$
c. $S{O_3}$
d. $C{O_2}$

Answer 1

Acid rain is a form of precipitation which, according to the Environmental Protection Agency or EPA contains high amounts of acidic components like Sulfuric acid and Nitric acid. It also contains invisible gases which is very harmful for our environment and is known to cause death of aquatic life forms, infertility in soil, corrosion of steel among others.

Complete answer:
$N{O_3}$ or $NO_3^ -$ is the chemical name of Nitrate ion. It is formed when Nitric acid loses a proton.

$S{O_2}$or Sulphur dioxide is liberated into the atmosphere in excess when we burn fossil fuels in power plants. The Sulphur present in the fossil fuels react with oxygen in the atmosphere to for Sulphur dioxide or $S{O_2}$, which in turn reacts with water to form Sulfuric acid or ${H_2}S{O_4}$.
${H_2}S{O_4}$ dissociates in presence of water giving ${H^ + }$ and $HSO_4^ -$ ions. The $HSO_4^ -$ can dissociate into $SO_4^{2 - }$ ion, that leads to an increased concentration of ${H^ + }$ in the rain water, leading to acid rain.

The equations can be summed up as:
$S{O_2} \to S{O_3} \to {H_2}S{O_4}$
${H_2}S{O_4} \to HSO_4^ - + {H^ + }$
$HSO_4^ - \to SO_4^{2 - } + {H^ + }$

$S{O_3}$ or Sulphur trioxide formed when Sulphur dioxide ($S{O_2}$) combines with atmospheric oxygen. $S{O_3}$ is a common pollutant that can cause respiratory problems like asthma and bronchitis.

$S + {O_2} \to S{O_2}$
$2S{O_2} + {O_2} \to 2S{O_3}$

$C{O_2}$ or Carbon dioxide is present in the atmosphere mainly due to combustion of fossil fuels in power generation, transport and residential sectors. $C{O_2}$ reacts with rain water to form carbonic acid (${H_2}C{O_3}$) - a weak acid. Therefore, the capacity of ${H_2}C{O_3}$ to cause acid rain is very limited.

Hence, the correct answer is option (B).

Additional information:
Acid rain is caused when the acidity of rain water increases. This happens both in natural and man-made ways. Natural causes of acid rain primarily include volcanic eruptions. However, the major cause of acid rain is the combustion of fossil fuel which is done by human beings to sustain life on earth. The effects of acid are very harmful for plants, animals, soils and even buildings and architectures. Acid rain can cause the plants to lose their protective covering and induce stunted growth. Soils can lose their fertility. Aquatic animals die because of the increased acidity of water bodies. We can reverse the effects of acid rain by restricting the use of fossil fuels and using sustainable sources of energy like solar energy and wind energy.

Note: Acid rain is caused when oxides of Sulphur and Nitrogen react with Oxygen from the atmosphere and form Sulfuric acid and Nitric acid. Acid rain is very harmful for life forms on the earth. It also depletes the soil of its fertility, causing destruction of vegetation. Acid Rain can also cause corrosion of marble monuments and steel structures. We can reverse the effects of acid rain by using renewable sources of energy like solar energy and wind energy.