Question

Which gas has the highest partial pressure atmosphere?
A) CO$_2$
B) H$_2$O
C) O$_2$
D) N$_2$

Answer 1

Hint: The concept of partial pressure in gases was proposed by Dalton, so it is named as Dalton’s law of Partial Pressures. The total pressure is the sum of the partial pressure of gases present in the mixture. It helps in predicting the movement of gases. It relates directly to the mole fraction of gases. So, find out the mole fraction of given gases.

Complete step by step answer:
Now, let us know about the partial pressure, consider a container containing a mixture of gases. All the gases present in a container contribute towards the total pressure of the gas. Partial pressure is the pressure exerted by an individual gas in a mixture.
We can say that pressure exerted in a mixture by gas will be the same as if it occupies the volume of the mixture at the same temperature.
As we know, the atmosphere consists of a mixture of gases, i.e. nitrogen, oxygen, carbon dioxide, water vapours, and other gases.
Among these gases, nitrogen constitutes 78% of the atmosphere or the gaseous mixture.
Thus, the mole fraction of nitrogen is the largest in the atmosphere.
As mentioned, a mole fraction is directly proportional to the partial pressure of the gas. Therefore, the larger the mole fraction, the higher the partial pressure.
Thus, we can conclude that N$_2$ gas is the highest partial pressure atmosphere.

The correct option is (D).

Note: The partial pressure and the total pressure are two different terms. Partial pressure depicts the thermodynamic relation of the gas molecules, whereas total pressure is dependent on the partial pressure.