Question

Which of the following does not contribute to acid rain?
(A) Nitrogen monoxide
(B) Sulphur dioxide
(C) Carbon monoxide
(D) Carbon dioxide

Answer 1

Hint: Acid rain is caused by the dissolution of oxides into the water molecules of rain in the atmosphere. The oxide dissolves in the water and forms acid. The acid rain is corrosive. For determining which compounds do not contribute to acid rain, we need to check which one of them won't convert into acid after reacting with oxygen and moisture present in the atmosphere.

Complete step by step solution:
We have been provided four gases: Nitrogen monoxide, Sulphur dioxide, Carbon monoxide, and Carbon dioxide.
We need to determine which of them would not contribute to acid rain.

So, for that,
First, we have a nitrogen monoxide:
Nitrogen monoxide reacting with atmospheric oxygen will result in the formation of nitrogen dioxide, which would further if come in contact with water forms nitric acid. So, it would contribute to acid rain.
$\begin{align}
 & \text{ }NO+{{O}_{2}}\to N{{O}_{2}} \\
 & 2N{{O}_{2}}+{{H}_{2}}O\to HN{{O}_{3}}+HN{{O}_{2}}\text{ } \\
\end{align}$

Next, we have sulphur dioxide:
Sulphur dioxide reacting with atmospheric oxygen will result in the formation of sulphur trioxide, which would further if come in contact with water forms sulphuric acid. So, it would contribute to acid rain.
$\begin{align}
 & \text{ }2S{{O}_{2}}+{{O}_{2}}\to 2S{{O}_{3}} \\
 & S{{O}_{3}}+{{H}_{2}}O\to {{H}_{2}}S{{O}_{4}}\text{ } \\
\end{align}$

Next, we have carbon monoxide:
Carbon monoxide does not react with water to form an acid. So, it would not contribute to acid rain.

The last one is carbon dioxide:
Carbon dioxide reacts with water to form carbonic acid thus contributing to acid rain.
$\text{ }C{{O}_{2}}+{{H}_{2}}O\to {{H}_{2}}C{{O}_{3}}\text{ }$
So, from all these gases only carbon monoxide does not react with water to form an acid. Thus, not contributing to the acid rain,
So, the correct answer is “Option C”.

Note: Naturally ‘clean’ rainwater is slightly acidic. It has a $\text{ pH }$ value equal to $\text{ 5}\text{.7 }$ this is because of the dissolution of the carbon dioxide to form carbonic acid. The oxides of Sulphur and nitrogen decrease $\text{ pH }$. Acid rain has an adverse effect on the environment. The acidic water reduces the fertility of the soil and the consumption of such water has serious health effects.