The compression factor

The compression factor:
The deviations of a real gas from ideal gas behaviour may be quantified by a parameter called the compression factor, usually given the symbol Z. At a given pressure and temperature, attractive and repulsive intermolecular forces between gas particles mean that the molar volume is likely to be smaller or larger than for an ideal gas under the same conditions. The compression factor is simply the ratio of the molar volume Vm of the gas to the molar volume Vm o of an ideal gas at the
same pressure and temperature.
The value of Z provides information on the dominant types of intermolecular forces acting in a gas.
Z = 1 No intermolecular forces, ideal gas behaviour
Z < 1 Attractive forces dominate, gas occupies a smaller volume than an ideal gas.
Z > 1 Repulsive forces dominate, gas occupies a larger volume than an ideal gas.
All gases approach Z=1 at very low pressures, when the spacing between particles is large on average.
The previous laws all assume that the gas being measured is an ideal gas, a gas that obeys them all exactly. But over a wide range of temperature, pressure, and volume, real gases deviate slightly from ideal. Since, according to Avogadro, the same volumes of gas contain the same number of moles, chemists could now determine the formulas of gaseous elements and their formula masses. The idea gas law is:
PV = nRT
Where n is the number of moles of the number of moles and R is a constant called the universal gas constant and is equal to approximately 0.0821 L-atm / mole-K.