ICSE Class 10 Answered

The amount or volume of nitrogen gas inhaled by the body is equal to the amount of nitrogen gas exhaled by the body. This is because nitrogen is not used by the body for any of the physiological processes. When you breathe in, nitrogen gas enters the bloodstream and circulates around the body without being used up or added to. When it reaches the lungs, it passes out again. 

However, there is a difference in the percentage of nitrogen inhaled and exhaled. The percentage of a gas in a mixture can vary, although the actual amount or volume of the gas remains the same. For example, consider in a bottle containing a mixture of 20% oxygen and 80% nitrogen. If we use a chemical to absorb all the oxygen in the bottle, the nitrogen left in the bottle would now be 100% of the gas present in the bottle. However, the amount or volume of nitrogen gas would still be the same. Similarly, when you consider the mixture of gases that enters inside the lungs, oxygen is absorbed by the body while more of carbon dioxide is released. This brings about a change in the percentage composition of these gases and ultimately affects the percentage composition of nitrogen gas. That is why, the percentage of nitrogen in inhaled and exhaled air is slightly different.