Introduction to Real Gas Behavior

Real gas behavior refers to the behavior of gases that deviate from the ideal gas law. The ideal gas law assumes that gases are composed of small, point-like particles that have no volume, have no attraction or repulsion to each other, and undergo completely elastic collisions. However, real gases do have volume, do exhibit attraction or repulsion to each other, and do not undergo completely elastic collisions. As such, the behavior of real gases can be quite different from that assumed by the ideal gas law.

Deviations from Ideal Gas Behavior

The behavior of real gases can deviate from ideal gas behavior in a number of ways. One common deviation is due to the volume occupied by the gas molecules themselves. Because gas molecules have a finite size, they can take up space and reduce the available space for other gas molecules to move around. This can lead to a reduction in the pressure and an increase in the volume of the gas, compared to what would be expected from the ideal gas law.

Another common deviation from ideal gas behavior is due to the attractive forces between gas molecules. Attractive forces can cause gas molecules to stick together, reducing the number of collisions with the walls of the container and reducing the pressure of the gas. This effect is particularly pronounced at low temperatures and high pressures, where the attractive forces are stronger.

Factors Affecting Real Gas Behavior

There are several factors that can affect the behavior of real gases. Temperature, pressure, and molecular size are all important factors. At low temperatures and high pressures, the attractive forces between gas molecules become more significant, leading to greater deviations from ideal gas behavior. Larger gas molecules also tend to exhibit greater deviations from ideal gas behavior, because they take up more space and have more opportunities for attractive forces to occur.

Example of Real Gas Behavior: Van der Waals Equation

The Van der Waals equation is a commonly used equation to describe the behavior of real gases. It takes into account the volume occupied by gas molecules as well as the attractive forces between them. The equation is:

(P + a(n/V)^2)(V – nb) = nRT

Where P is the pressure, V is the volume, n is the number of moles of gas, R is the gas constant, T is the temperature, a is a constant to account for the attractive forces between the gas molecules, and b is a constant to account for the volume occupied by the gas molecules themselves.

The Van der Waals equation is useful because it can more accurately predict the behavior of real gases, particularly at high pressures and low temperatures, where attractive forces and molecular size become more significant. It is an important tool for understanding the behavior of real gases in many different contexts, from industrial processes to atmospheric science.