1: Introduction to Physical Chemistry using Gases
- Page ID
- 339631
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Gases comprise a very important type of system that can be modeled using thermodynamics. This is true because gas samples can be described by very simple equations of state, such as the ideal gas law. In this chapter, both macroscopic and microscopic descriptions of gases will be used to demonstrate some of the important tools of thermodynamics.
- 1.1: Prior Knowledge of Chemistry, Math, and Physics
- Physical Chemistry has many prerequisites from chemistry, math, and physics. We will utilize skills you have already built in those other classes throughout the course! But don't worry, you aren't expected to remember everything from those courses. We will refresh prior knowledge as we need it!
- 1.2: Integrating Macroscopic, Microscopic, and Mathematical Approaches
- Physical chemistry involves combining multiple ways of thinking through problems. We will think through problems using macroscopic, microscopic, and mathematical models. It is important for us to connect all of these together so we don't get bogged down in the math and lose our connection to chemistry.
- 1.3: The Ideal Gas Law
- The ideal gas law combines the empirical laws into a single expression. It also predicts the existence of a single, universal gas constant, which turns out to be one of the most important fundamental constants in science. As derived here, it is based entirely on empirical data. It represents “limiting ideal behavior.” As such, deviations from the behavior suggested by the ideal gas law can be understood in terms of what conditions are required for ideal behavior to be followed (or approached).
- 1.4: The Kinetic Molecular Theory of Gases
- The gas laws were derived from empirical observations. Connecting them to fundamental properties of the gas particles is subject of great interest. The Kinetic Molecular Theory is one such approach. In its modern form, the Kinetic Molecular Theory of gasses is based on five basic postulates.
- 1.5: Kinetic Energy
- It is also important to recognize that the most probable, average, and RMS kinetic energy terms that can be derived from the Kinetic Molecular Theory do not depend on the mass of the molecules. As such, it can be concluded that the average kinetic energy of the molecules in a thermalized sample of gas depends only on the temperature. However, the average speed depends on the molecular mass. So, for a given temperature, light molecules will travel faster on average than heavier molecules.
- 1.6: Ideal Gas Law as a Model
- The ideal gas law is a model for how gases behave under certain well-defined assumptions. By seeing how experimental data differs from ideal gas law calculations, we can learn something about how the gas molecules are interacting with each other. The assumptions for the ideal gas law are clearly never "true", but by setting this well-defined idealized reference we can learn a lot of information.
- 1.7: Real Gases
- While the ideal gas law is sufficient for the prediction of large numbers of properties and behaviors for gases, there are a number of times that deviations from ideality are extremely important.
- 1.E: Gases (Exercises)
- Exercises for Chapter 2 "Gases" in Fleming's Physical Chemistry Textmap.
- 1.S: Gases (Summary)
- Summary for Chapter 2 "Gases" in Fleming's Physical Chemistry Textmap.
Contributor
Patrick E. Fleming (Department of Chemistry and Biochemistry; California State University, East Bay)