Compressibility factor (Z)

Definition

The compressibility factor (Z) is a measure of how much the behavior of a real gas deviates from an ideal gas. It is defined as the ratio $Z = \frac{PV}{nRT}$.

5 Must Know Facts For Your Next Test

1. The compressibility factor (Z) equals 1 for an ideal gas.
2. When Z > 1, the gas is less compressible than an ideal gas due to repulsive forces.
3. When Z < 1, the gas is more compressible than an ideal gas due to attractive forces.
4. Real gases deviate more from ideal behavior at high pressures and low temperatures.
5. The van der Waals equation accounts for deviations in real gases by introducing parameters 'a' and 'b'.

Review Questions

• What does a compressibility factor (Z) value greater than 1 indicate about a gas?
• How is the compressibility factor (Z) calculated?
• In what conditions do real gases exhibit significant deviations from ideal behavior?

Related terms

Ideal Gas Law: A fundamental equation $PV = nRT$ that describes the relationship between pressure, volume, temperature, and number of moles for an ideal gas.

van der Waals Equation: An equation that adjusts the Ideal Gas Law to account for intermolecular forces and molecular volumes: $(P + \frac{a}{V^2})(V - b) = nRT$.

Boyle's Law: A law stating that at constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume: $P_1V_1 = P_2V_2$.