Final answer:
If the volume of a gas is greater than expected based on the ideal gas law, it is because the molecules of a real gas have small but measurable volumes. If the volume of a gas is less than expected based on the ideal gas law, it is because the molecules of an ideal gas are assumed to have zero volume.
Step-by-step explanation:
If the volume of a gas is greater than you would expect based on the ideal gas law, the best explanation for this is because the molecules of a real gas have small but measurable volumes. At low pressures, the gaseous molecules are relatively far apart, but as the pressure of the gas increases, the intermolecular distances become smaller and smaller. As a result, the volume occupied by the molecules becomes significant compared with the volume of the container. Consequently, the total volume occupied by the gas is greater than the volume predicted by the ideal gas law.
If the volume of a gas is less than you would expect based on the ideal gas law, the best explanation for this is because the molecules of an ideal gas are assumed to have zero volume. In the ideal gas model, the volume occupied by its atoms and molecules is a negligible fraction of V. Thus, the ideal gas law predicts that the volume of a gas is solely determined by the volume of the container. However, in reality, the molecules of a real gas have small but measurable volumes. Therefore, the total volume occupied by the gas is less than the volume predicted by the ideal gas law.