Real Gases

Definition

Real gases are gases that exhibit behavior that deviates from the ideal gas law, which assumes that gas molecules have no volume and do not interact with each other. Real gases account for the actual properties of gas molecules, such as their finite size and intermolecular attractive forces, which become significant at high pressures and low temperatures.

5 Must Know Facts For Your Next Test

1. Real gases deviate from ideal gas behavior due to the finite size of gas molecules and the attractive forces between them.
2. The Van der Waals equation is a modified version of the ideal gas law that accounts for these non-ideal gas properties.
3. The compressibility factor, Z, is used to quantify the deviation of a real gas from ideal gas behavior, with Z = 1 indicating ideal gas behavior.
4. Real gases exhibit more complex behavior, such as the ability to liquefy and the presence of critical points, which are not captured by the ideal gas law.
5. The behavior of real gases is particularly important at high pressures and low temperatures, where the deviations from ideal gas behavior become more significant.

Review Questions

• Explain the key differences between the behavior of real gases and ideal gases.
  • The primary differences between real gases and ideal gases are that real gases account for the finite size of gas molecules and the attractive forces between them. Ideal gases are assumed to have no volume and no intermolecular interactions, which is not the case for real gases. As a result, real gases exhibit more complex behavior, such as the ability to liquefy and the presence of critical points, which are not captured by the simple ideal gas law. The Van der Waals equation is a modified version of the ideal gas law that takes these non-ideal gas properties into account, providing a more accurate description of real gas behavior, particularly at high pressures and low temperatures.
• Describe the role of the compressibility factor, Z, in characterizing real gas behavior.
  • The compressibility factor, Z, is a dimensionless quantity that measures the deviation of a real gas from ideal gas behavior. When Z = 1, the gas exhibits ideal gas behavior, meaning it follows the simple relationships described by the ideal gas law. However, for real gases, Z is typically less than 1, indicating that the gas is less compressible than an ideal gas due to the finite size of the gas molecules and the attractive forces between them. The value of Z can vary significantly depending on the gas, temperature, and pressure, and it is an important parameter for accurately describing and predicting the behavior of real gases, particularly in applications where high pressures or low temperatures are involved.
• Analyze the implications of real gas behavior on the design and operation of practical systems, such as refrigeration or compressed gas storage.
  • The behavior of real gases has significant implications for the design and operation of practical systems that involve gases under high pressure or low temperature conditions. For example, in refrigeration systems, the liquefaction and critical point behavior of real gases must be carefully considered to ensure efficient and safe operation. Similarly, in the storage and transportation of compressed gases, the deviations from ideal gas behavior can affect the volume and pressure requirements, as well as the potential for liquefaction or phase changes. Understanding the compressibility factor and other real gas properties is crucial for engineers and scientists to accurately model, design, and optimize these types of systems, ensuring their reliable and efficient performance.

Related terms

Ideal Gas Law: The ideal gas law is a simple mathematical relationship that describes the behavior of an ideal gas, relating the pressure, volume, amount of substance, and absolute temperature.

Van der Waals Equation: The Van der Waals equation is a modified version of the ideal gas law that takes into account the finite size of gas molecules and the attractive forces between them, providing a more accurate description of real gas behavior.

Compressibility Factor: The compressibility factor is a dimensionless quantity that measures the deviation of a real gas from ideal gas behavior, with a value of 1 indicating ideal gas behavior.