3. Ideal and Real Gasses

# 3.0 Chapter introduction and learning objectives

Thermodynamic tables are commonly used to evaluate thermodynamic properties of a pure substance. This method is accurate, but may be time consuming for complicated calculations. It would be desirable if, for some special cases, a simple method with relatively good accuracy could be developed for evaluating thermodynamic properties.

This chapter introduces the concepts of “ideal” gas, ideal gas equation of state (EOS), real gas, and compressibility factor. It explains the difference between “ideal” and real gases, and at what conditions the ideal gas model may be used as an approximation for evaluating thermodynamic properties of simple gases.

Learning Objectives

After completing the module, you should be able to

• Understand the limitation of the ideal gas equation of state
• Apply the ideal gas equation of state in solving engineering problems as appropriate
• Explain the difference between “ideal” and real gases
• Calculate the compressibility factor of a pure substance at a given state
• Identify if a substance may be treated as an ideal or real gas for a given condition based on its compressibility factor