Real Gases

Definition

Real gases refer to the behavior of gases that deviate from the ideal gas model, taking into account the finite size of gas molecules and the attractive and repulsive forces between them. This is in contrast to the idealized behavior described by the Ideal Gas Law, which assumes gas molecules are point-like particles with no volume and no intermolecular interactions.

5 Must Know Facts For Your Next Test

1. Real gases exhibit deviations from the Ideal Gas Law at high pressures and low temperatures, where the finite size of gas molecules and intermolecular forces become significant.
2. The Van der Waals equation is a more accurate model for real gases, incorporating terms for the finite volume of gas molecules and the attractive forces between them.
3. The compressibility factor, $Z$, is used to quantify the deviation of a real gas from ideal gas behavior, where $Z = 1$ for an ideal gas and $Z < 1$ or $Z > 1$ for a real gas.
4. Real gases tend to be less compressible than ideal gases due to the repulsive forces between gas molecules at high pressures.
5. The behavior of real gases approaches that of an ideal gas as the pressure decreases and the temperature increases, where the intermolecular forces become negligible.

Review Questions

• Explain how the behavior of real gases differs from that of ideal gases, and describe the factors that contribute to this deviation.
  • The behavior of real gases differs from ideal gases due to the finite size of gas molecules and the attractive and repulsive forces between them. Unlike ideal gases, which are assumed to be point-like particles with no volume and no intermolecular interactions, real gases exhibit deviations from the Ideal Gas Law, especially at high pressures and low temperatures. These deviations are accounted for in the Van der Waals equation, which includes terms for the finite volume of gas molecules and the attractive forces between them. The compressibility factor, $Z$, is used to quantify the degree to which a real gas deviates from ideal gas behavior, with $Z < 1$ indicating the gas is less compressible than an ideal gas due to the repulsive forces between molecules at high pressures.
• Describe the relationship between the Ideal Gas Law and the behavior of real gases, and explain how the Van der Waals equation provides a more accurate model for real gas behavior.
  • The Ideal Gas Law, $PV = nRT$, provides a simplified model for the behavior of gases, assuming gas molecules have no volume and no intermolecular interactions. However, at high pressures and low temperatures, real gases exhibit deviations from this ideal behavior due to the finite size of gas molecules and the attractive and repulsive forces between them. The Van der Waals equation, $ extbackslashleft(P + rac{a}{V^2} extbackslashright)(V - b) = nRT$, where $a$ and $b$ are constants that account for the intermolecular forces and the finite volume of gas molecules, respectively, provides a more accurate model for real gas behavior. By incorporating these additional terms, the Van der Waals equation can better describe the compressibility and other properties of real gases, especially under conditions where the Ideal Gas Law breaks down.
• Analyze the role of the compressibility factor, $Z$, in understanding the behavior of real gases, and explain how it can be used to compare the behavior of real gases to that of ideal gases.
  • The compressibility factor, $Z$, is a dimensionless quantity that quantifies the deviation of a real gas from ideal gas behavior. It is defined as the ratio of the actual volume of the gas to the volume predicted by the Ideal Gas Law, $Z = rac{PV}{nRT}$. For an ideal gas, $Z = 1$, indicating the gas follows the Ideal Gas Law exactly. For a real gas, $Z$ can be less than 1 or greater than 1, depending on the relative strength of the attractive and repulsive forces between gas molecules. A $Z$ value less than 1 indicates the real gas is less compressible than an ideal gas, due to the repulsive forces between molecules at high pressures. Conversely, a $Z$ value greater than 1 suggests the real gas is more compressible than an ideal gas, due to the attractive forces between molecules. By analyzing the compressibility factor, researchers can better understand the behavior of real gases and how it deviates from the idealized model described by the Ideal Gas Law.

Related terms

Ideal Gas: An idealized gas that follows the Ideal Gas Law, assuming gas molecules have no volume and no intermolecular interactions.

Van der Waals Equation: A modified version of the Ideal Gas Law that accounts for the finite size of gas molecules and the attractive forces between them.

Compressibility Factor: A measure of how much a real gas deviates from the behavior of an ideal gas, calculated as the ratio of the actual volume to the volume predicted by the Ideal Gas Law.