Compressibility factor of a gas is

Solution (By Examveda Team)

The compressibility factor (Z) is defined as Z = PV / nRT, which measures the deviation of a real gas from ideal gas behavior.

For an ideal gas, the relation PV = nRT holds exactly. Substituting into the expression for Z gives Z = 1. Thus, the compressibility factor is exactly unity when the gas follows the ideal gas law.

Real gases, however, deviate from ideal behavior due to intermolecular forces and finite molecular volumes. In such cases, Z ≠ 1, and its value depends on the pressure, temperature, and nature of the gas.

Option A: Incorrect, because Z does vary with pressure for real gases.

Option B: Incorrect, because Z depends on the nature of the gas.

Option C: Incorrect, because Z also varies with temperature.

Option D: Correct, because Z = 1 only when the gas behaves ideally according to PV = nRT.

Therefore, the compressibility factor of a gas is unity if it follows PV = nRT.