Non-ideal behavior

Definition

Non-ideal behavior refers to the deviations of real gases from the ideal gas laws, which assume that gas particles do not interact and occupy no volume. In reality, interactions between molecules and the volume they occupy become significant, especially under high pressure and low temperature conditions. This behavior is essential to understand when analyzing gas mixtures since it affects properties like pressure, temperature, and composition.

5 Must Know Facts For Your Next Test

1. Non-ideal behavior is most noticeable in gases at high pressures where molecules are closer together, leading to increased intermolecular forces.
2. Low temperatures can also induce non-ideal behavior because the kinetic energy of gas molecules decreases, allowing attractive forces to take effect.
3. The van der Waals equation is an example of an adjustment to the ideal gas law that accounts for non-ideal behavior by introducing parameters for molecular volume and attraction.
4. In a mixture of gases, the non-ideal behavior can result in unexpected changes in properties like partial pressures and overall system pressure due to interactions between different gas species.
5. The degree of non-ideal behavior can be quantified using the compressibility factor (Z), which helps predict how a real gas will behave under varying conditions compared to an ideal gas.

Review Questions

• How does non-ideal behavior affect the properties of a gas mixture under high pressure?
  • Under high pressure, gas molecules are forced closer together, leading to significant intermolecular interactions that are not accounted for in the ideal gas law. This results in deviations from expected values for pressure and volume. For example, the attractive forces between molecules can reduce the pressure exerted by the gas mixture compared to what would be predicted if it were behaving ideally.
• Discuss how the van der Waals equation addresses non-ideal behavior in gases.
  • The van der Waals equation modifies the ideal gas law by incorporating two constants: 'a,' which accounts for intermolecular forces, and 'b,' which accounts for the finite volume of gas molecules. By including these parameters, the van der Waals equation provides a more accurate description of real gas behavior under various conditions. This is crucial for understanding how gases behave in mixtures where interactions can significantly impact their collective properties.
• Evaluate the implications of non-ideal behavior on calculating the properties of gas mixtures in engineering applications.
  • In engineering applications, accurately calculating the properties of gas mixtures is critical for processes such as combustion, refrigeration, and chemical reactions. Non-ideal behavior complicates these calculations because it affects how different gases interact with each other. Using models like the compressibility factor allows engineers to adjust their calculations based on real behavior rather than assuming ideality. This ensures better design and efficiency in systems where precise predictions are necessary.

Related terms

Ideal Gas Law: A fundamental equation of state for gases represented as PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature.

Real Gas: A gas that does not follow the ideal gas law due to intermolecular forces and finite molecular volume, particularly at high pressures and low temperatures.

Compressibility Factor (Z): A dimensionless quantity that describes how much a real gas deviates from ideal behavior, defined as Z = PV/nRT; values of Z different from 1 indicate non-ideal behavior.