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Ideal Gas Law

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Ideal Gas Law


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You will learn about the ideal gas law and the relationship among the variables in the ideal gas law.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Explain how Boyle’s law, Charles’ law, and Avogadro’s law are part of the ideal gas law.
  • State the meaning of each symbol in the ideal gas law.
  • Describe the relationship among pressure, volume, and temperature.
  • Explain how the number of moles of a gas affects pressure, volume, and temperature of the gas.
  • Describe the relationship between temperature and the product of pressure and volume as a direct relationship.

Everything You'll Have Covered

The ideal gas law expresses a relationship among pressure, volume, temperature, and the number of moles of a gas. It is a combination of three gas laws: Boyle's law (PV = k), Charles' law (V/T = k), and Avogadro's law (V/n = k). It states that any two gases that have equal volume and are at the same pressure and temperature will have an equal number of moles.

In an ideal gas, all collisions of particles are elastic and intermolecular interactions are nonexistent. Ideal gases are theoretical, but most real gases act nearly ideally under normal conditions. The behavior of a gas can deviate if it is under high pressure or low temperature. When a gas is subjected to high pressure the distance between the molecules decreases. This allows the intermolecular forces to have a greater influence on the behavior of molecules. Gases also deviate from ideal gas behavior when they are at low temperatures. This is because gas molecules slow to the point that intermolecular interactions become more significant.

The ideal gas law is expressed as PV = nRT. This means that as the product of pressure and volume increases, the product of moles and temperature must also increase. The R in the ideal gas law stands for the gas law constant 0.0821 L atm/mol K. Because of the units for the gas constant, pressure needs to be expressed in terms of atmospheres, volume in liters, and temperature in Kelvin. Using this equation, one can predict what will happen to one variable if another is changed.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Learners should be familiar with Avogadro’s Law, Boyle’s Law, Charles’ Law, kinetic molecular theory, and the mole.
Course Chemistry
Type of Tutorial Concept Development
Key Vocabulary Amedeo Avogadro, constant, compression