Which statement is an ideal gas assumption?

Which statement is an ideal gas assumption?

• A. Volume is insignificant.
• B. Collisions are inelastic.
• C. Average kinetic energy depends on pressure.
• D. Gases have strong attractive forces.

Answer: (A)

At the heart of the ideal gas model is the idea that gas particles are point-like, with negligible size and no significant intermolecular attractions, and that their collisions are perfectly elastic. Saying volume is insignificant aligns with this: the actual size of the molecules is so small compared to the container that the gas volume is effectively the container’s volume. This lets properties depend on how many particles, the temperature, and the container size relate to each other, which is why gas behavior is captured by PV = nRT rather than by the molecules’ sizes. The other statements clash with this picture. If collisions were inelastic, kinetic energy would not be conserved during collisions, which isn’t assumed in the ideal model. If average kinetic energy depended on pressure, that would imply a direct pressure effect on molecular motion beyond temperature, contradicting the idea that KE is set by temperature alone. If gases had strong attractive forces, those interactions would influence behavior and prevent the gas from acting ideally, especially at high pressures or low temperatures.

At the heart of the ideal gas model is the idea that gas particles are point-like, with negligible size and no significant intermolecular attractions, and that their collisions are perfectly elastic. Saying volume is insignificant aligns with this: the actual size of the molecules is so small compared to the container that the gas volume is effectively the container’s volume. This lets properties depend on how many particles, the temperature, and the container size relate to each other, which is why gas behavior is captured by PV = nRT rather than by the molecules’ sizes.

The other statements clash with this picture. If collisions were inelastic, kinetic energy would not be conserved during collisions, which isn’t assumed in the ideal model. If average kinetic energy depended on pressure, that would imply a direct pressure effect on molecular motion beyond temperature, contradicting the idea that KE is set by temperature alone. If gases had strong attractive forces, those interactions would influence behavior and prevent the gas from acting ideally, especially at high pressures or low temperatures.