What does the compressibility factor (Z) measure in gases?

The compressibility factor (Z) is a critical parameter in understanding how real gases deviate from the ideal gas behavior described by the ideal gas law. For an ideal gas, the compressibility factor is equal to 1, indicating that the gas follows the ideal gas law perfectly under all conditions. However, real gases exhibit interactions between particles and occupy finite volume, especially under high pressure or low temperature conditions.

When Z is greater than 1, it indicates that the gas is less compressible than predicted by the ideal gas law, often due to repulsive forces between gas molecules at high pressures. Conversely, a Z value less than 1 suggests that the gas is more compressible, typically indicating attractive forces among particles that become significant at higher densities. Thus, the compressibility factor serves as a measure of the extent to which a gas deviates from ideal behavior, revealing insights into the intermolecular forces and the conditions under which the gas exists. This makes it a valuable tool in both theoretical calculations and practical applications involving real gases.