Daviation of real gases from Ideal behavior

⚫Intoduction:

Ideal gases are theoretical gases that follow the ideal gas law, which describes their behavior in terms of pressure, volume, temperature, and the number of molecules. However, real gases do not always behave according to the ideal gas law, especially at high pressures and low temperatures. This deviation from ideal behavior is due to several factors, including the size and shape of the gas molecules, the intermolecular forces between the molecules, and the compressibility of the gas.

⚫Factor - Size and Shape:

One of the main factors that affect the behavior of real gases is the size and shape of the gas molecules. In an ideal gas, the molecules are treated as point masses with no volume, so they do not interact with each other except through elastic collisions. However, real gas molecules have a finite size and volume, which means they can collide with each other and with the walls of the container. This reduces the effective volume of the gas and increases the pressure, leading to a deviation from ideal behavior.

⚫Factor - Intermolecular Force:

Another factor that affects the behavior of real gases is the intermolecular forces between the molecules. In an ideal gas, the molecules have no attractive or repulsive forces between them, so they do not stick together or clump up. However, in real gases, the molecules do interact with each other through van der Waals forces, dipole-dipole interactions, and hydrogen bonding. These forces can cause the gas molecules to stick together and form clusters, which reduces the effective volume of the gas and increases the pressure.

⚫Factor - Compressibility:

The compressibility of the gas also affects its behavior. In an ideal gas, the molecules are assumed to be infinitely compressible, so their volume can be reduced to zero. However, in real gases, the molecules have a finite compressibility, which means they resist compression and require more pressure to be squeezed into a smaller volume. This leads to a deviation from ideal behavior, especially at high pressures.

⚫Formula used for real gases:

To account for these deviations from ideal behavior, several modifications have been made to the ideal gas law. The most common modification is the van der Waals equation, which includes two correction factors for the volume and pressure of the gas:

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Here, P is the pressure of the gas, V is its volume, n is the number of moles of the gas, R is the gas constant, T is the temperature of the gas in kelvins, a is the van der Waals constant for the intermolecular forces, and b is the van der Waals constant for the size of the gas molecules.

The van der Waals equation accounts for the attractive and repulsive forces between the gas molecules and the finite size of the molecules. Other equations of state, such as the Redlich-Kwong equation and the Peng-Robinson equation, also include correction factors for deviations from ideal behavior.

⚫Conclusion:

In conclusion, real gases do not always behave according to the ideal gas law due to the size and shape of the gas molecules, the intermolecular forces between the molecules, and the compressibility of the gas. These deviations from ideal behavior can be accounted for by modifying the ideal gas law using equations of state that include correction factors for the volume, pressure, and other properties of the gas.