ACS Physical Chemistry: Thermochemistry Practice Test 2026 - Free Thermochemistry Practice Questions and Study Guide

When the compressibility factor (Z) of a gas is greater than 1, it indicates that the gas is less compressible than predicted by the ideal gas law. This situation typically arises in conditions where repulsive forces between gas molecules are significant.

In the context of intermolecular forces, repulsion occurs when gas molecules are forced closer together than their natural separation, which happens at high pressures or low temperatures. In this scenario, the volume occupied by the gas is greater than what would be expected for an ideal gas, which aligns with the observation that Z is greater than 1. This illustrates that the molecules are resisting compression more than ideal behavior would suggest, primarily due to these repulsive interactions.

Thus, the correct answer highlights the significance of repulsive forces in affecting the behavior of real gases under certain conditions, underscoring how deviations from ideal gas behavior can be linked to molecular interactions and forces.