Real Gas vs Ideal Gas: Compressibility Ratio

[101nancyma]

The compressibility ratio of a gas is PV/nRT. What happen to the compressibility ratio if the attration force between the gas molecules increase? The answer says it decreases because the more molecules interact with each other, so the pressure they exert on the container decreases, thus compressibility ratio decreases. The part I don't understand is according to the real gas equation, real volume increases, and real pressure decreases. If it is true, then shouldn't the compressibility ration remain the same?

 

[Electrocuted]

You must note that though what you have thought is true, you have forgotten that when there is a change (delta) in the pressure and volume, you have to take into account the temperature change as well.

 

[sir-pinski]

The compressibility ratio is a measure of how easily a gas can be compressed. In an ideal gas, there are no interactions between molecules and the gas behaves according to the ideal gas law. In this case, the compressibility ratio is constant.

However, in a real gas, there are intermolecular interactions between the gas molecules. These interactions can be attractive or repulsive, depending on the type of gas and its conditions. When the attractive forces between gas molecules increase, the gas becomes more difficult to compress because the molecules are more strongly attracted to each other. This results in a decrease in pressure and an increase in volume, as you mentioned.

The decrease in pressure and increase in volume in a real gas does not necessarily mean that the compressibility ratio remains the same. This is because the compressibility ratio takes into account not only the volume and pressure changes, but also the amount of gas present (n), the temperature (T), and the gas constant (R). As the attractive forces between gas molecules increase, the gas becomes less compressible, meaning that the compressibility ratio decreases.

In summary, the compressibility ratio of a gas is affected by changes in pressure, volume, temperature, and the strength of intermolecular interactions. In the case of increasing attractive forces between gas molecules, the compressibility ratio decreases, indicating that the gas is less compressible.