Understanding Ideal Gas Behavior vs. Real Gas Deviation

The behavior of gases is often described by the ideal gas law, which is based on several assumptions about the nature of gas molecules. According to the ideal gas model, the gas molecules are considered point masses with no volume and there are no forces of attraction or repulsion between them. The collisions between molecules and the walls of the container are assumed to be perfectly elastic.

Why Real Gases Deviate from Ideal Gas Behavior

In reality, no gas is perfectly ideal. Real gases deviate from the ideal gas behavior, especially at high pressures and low temperatures. This deviation occurs because the assumptions of the ideal gas model are not completely valid for real gases. There are two main reasons for this deviation:

1. The volume occupied by the gas molecules themselves is not negligible compared to the total volume of the gas, particularly at high pressures where the molecules are closer together.
2. There are forces of attraction and repulsion between gas molecules, known as intermolecular forces.

The Impact of Intermolecular Forces on Real Gas Deviation

One of the primary reasons real gases deviate from ideal gas behavior is the presence of intermolecular forces. The ideal gas model assumes no forces exist between molecules. However, in real gases, molecules do exert attractive and repulsive forces on each other. At moderate to low temperatures and high pressures, these attractive forces become significant.

These attractive intermolecular forces reduce the pressure exerted by the gas compared to what would be expected for an ideal gas. This is because molecules hitting the walls of the container are pulled back slightly by the attractive forces from other molecules, reducing the momentum they transfer to the walls. The presence of these Intermolecular Forces is a key aspect of Real Gas Deviation from the predictions of the Kinetic Theory of Gases, which forms the basis for Ideal Gas Behavior.

While the volume of the molecules also contributes to Real Gas Deviation, the presence of Intermolecular Forces is a fundamental reason why real gases behave differently from ideal gases. The Kinetic Theory of Gases assumes point masses with no interaction, which is an oversimplification for real substances exhibiting Ideal Gas Behavior.

Therefore, gases deviate from the ideal gas behaviour largely because their molecules have forces of attraction between them.