Overview
Test Series
Compressibility refers to the ability of a substance to be condensed or squeezed into a smaller volume under the application of pressure. This behavior is typically attributable to the presence of spaces or pores within the substance, and the change in volume is a result of the pressure forcing these spaces to become smaller.
Among the three states of matter - solids, liquids, and gases, gases are the most compressible. This is due to the large amount of space between gas particles, as explained by the kinetic-molecular theory. At room temperature and standard pressure, the average distance between gas molecules is about ten times the diameter of the molecules themselves. When pressure is applied to a gas, the particles are forced closer together, resulting in compression.
Get 6 Months SuperCoaching @ just
₹1999₹499
Compression leads to changes in the properties of a gas. The most obvious of these changes is a reduction in the volume occupied by the gas. Depending on the conditions, compression may also alter the temperature and pressure of the gas.
In the Case of Ideal Gas
Compressing an ideal gas reduces its volume, as per the ideal gas law. This law also demonstrates how compression affects other properties of the gas:
This equation always holds true. If a certain amount of gas is compressed under constant temperature conditions (isothermic process), the pressure must increase to compensate for the reduced volume.
Similarly, when a gas is cooled (the temperature is reduced) under constant pressure, its volume decreases – it compresses.
The compressibility factor is a thermodynamic property that modifies the ideal gas equation to account for real gases.
The ideal gas equation for ideal gases is PV = nRT.
This equation can be adjusted for real gases as PV = ZnRT, where Z is the compressibility factor for the specific gas.
The compressibility of a gas is influenced by the nature of the gas itself, as well as the temperature and pressure conditions.
When Z = 1, the gas behaves like an ideal gas. Any deviation in the compressibility factor from 1 indicates that the gas is a real gas.
If Z > 1, repulsive forces are dominant.
If Z < 1, attractive forces are dominant.
The compressibility factor for Hydrogen (H2) is always greater than 1, indicating that Z > 1.
This is because the intermolecular attractive force in hydrogen is negligible due to its small size, and hence hydrogen predominantly exhibits repulsive forces. This results in actual volumes being greater than ideal values.
On the other hand, Oxygen (O2) has a compressibility factor of 0.308, which is less than 1, and critical pressures and volumes of 50.1atm and 0.078litre/mol, respectively.
Therefore, it can be concluded that Oxygen gas is more compressible than Hydrogen gas due to its compressibility factor being less than 1.
Download the Testbook APP & Get Pass Pro Max FREE for 7 Days
Download the testbook app and unlock advanced analytics.