What is Compressibility?
“Compressibility is the property of being compressed by pressure into a smaller space. This property is caused by porosity, and the change in bulk is caused by the pressure bringing the particles closer together.”
Gases are more compressible than liquids or solids, according to the kinetic-molecular theory. Gases are compressible because the majority of a gas’s volume is made up of large amounts of empty space between the gas particles. The average distance between gas molecules at room temperature and standard pressure is about ten times the diameter of the molecules themselves. The gas particles are forced closer together when a gas is compressed.
Table of Contents
- Applications of Compressibility of Gases
- Changes During Compression of Gases
- Compressibility Factor
- Why is Oxygen More Compressible than Hydrogen?
- Frequently Asked Questions – FAQs
Applications of Compressibility of Gases
- Compressed gases are used in a variety of applications.
- In hospitals, oxygen is frequently used to help patients breathe better.
- When a patient undergoes a major operation, the anaesthesia used is frequently compressed gas.
- Welding necessitates extremely hot flames generated by compressed acetylene and oxygen mixtures.
- A large amount of gas can be compressed in a small chamber and used, as in LPG (Liquefied Petroleum Gas) and CNG (Compressed Natural Gas). As a result, large volumes of gas can be transported and stored in a single-cylinder with ease.
- Cold drinks are another common application of gas compression. Gases that can be dissolved in liquids, such as carbon dioxide, are compressed in these drinks. These gases are kept at low temperatures and high pressures in order to remain dissolved in liquids.
Changes During Compression of Gases
Compressing a gas causes changes in its properties. The volume of space occupied by the gas decreases as it is compressed. Compression alters the temperature and pressure of the gas as well, depending on the circumstances.
In Ideal Gas
Since compressing something decreases its volume, compressing a gas decreases its volume. Rearranging the ideal gas law demonstrates how this affects other characteristics of the gas:
This equation is always correct. If you compress a fixed number of moles of gas in an isothermic process (one that stays at the same temperature), the pressure must rise to account for the smaller volume on the left side of the equation.
Similarly, when you cool a gas (reduce T) at constant pressure, its volume decreases – it compresses.
Compressibility Factor
The gas compressibility factor is a thermodynamic property that is used to modify the ideal gas equation for real gases.
PV = nRT is the ideal gas equation for ideal gases.
For real gases, this equation can be modified to read PV = ZnRT, where Z is the compressibility factor for the given gas.
The compressibility of a gas is determined by the gas itself, as well as the temperature and pressure conditions.
Why is Oxygen More Compressible than Hydrogen?
When Z = 1, the gases behave like an ideal gas, But any deviation in the compressibility factor makes the gas a real gas.
If Z > 1, repulsive forces are dominant
If Z < 1, attractive forces are dominant
The compressibility factor for H2 is always greater than one that is, Z > 1.
This is observed because the intermolecular attraction force is negligible due to its small size due to which hydrogen exhibits intermolecular repulsive forces, causing actual volumes to be greater than ideal values.
Oxygen (O2) has a compressibility factor of 0.308 which is Z < 1, and critical pressures and volumes of 50.1atm and 0.078litre/mol, respectively.
Thus, we can conclude that Oxygen gas is more compressible than Hydrogen gas due to its compressibility factor being lesser than 1.
Frequently Asked Questions on O2 is More Compressible Than H2
Why is it that gases are more compressible than solids and liquids?
Gases are more compressible than liquids or solids, according to the kinetic-molecular theory. Gases are compressible because the majority of a gas’s volume is made up of large amounts of empty space between the gas particles.
Why are hydrogen and helium so difficult to compress?
Due to the extremely weak attractive forces between hydrogen molecules or helium atoms, they cannot liquefy unless extremely cold. Because their molecules are so light, they are difficult to compress to a density comparable to other gases.
What happens when oxygen becomes compressed?
If you compress oxygen sufficiently, it liquefies, and the density of liquid oxygen is approximately 1140 kg/m3. This results in an oxygen molecule spacing of about 0.35nm.
Name the heaviest and the lightest gas.
The heaviest gas is Radon, and the lightest gas is Hydrogen.
Which forces are dominant when the value of Z deviates unity.
Inter-molecular attractive and repulsive forces cause deviations in the compressibility factor z from one.
When Z > 1, repulsive forces are dominant and when Z < 1, attractive forces are dominant.
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