Which condition makes real gases behave most like ideal gases?

• A. High pressure and low temperature.
• B. Low pressure and high temperature.
• C. Very high density of the gas.
• D. Gases always behave as ideal.

Answer: (B)

Real gas behavior aligns with the ideal gas law when the particles interact very little and occupy almost no volume compared with the container. This happens most when the gas is at low pressure and high temperature. At low pressure, molecules are far apart, so intermolecular attractions and repulsions are weak. At high temperature, the molecules move rapidly, and their kinetic energy overwhelms any residual attractions, making collisions effectively elastic and the volume of the molecules themselves negligible relative to the container. In contrast, high pressure or high density brings molecules closer together, increasing interactions and the finite size of particles, which causes real gases to deviate from ideal behavior. So, the best condition is low pressure and high temperature.