http://www.ck12.org Chapter 14. The Behavior of Gases
14.3 Ideal Gases
Lesson Objectives
- Know the ideal gas law, and know which of the different values for the ideal gas constant to use in a given
situation. - Use the ideal gas law to calculate the pressure, volume, temperature, or number of moles of an ideal gas when
the other three quantities are known. - Use the ideal gas law to calculate the molar mass or the density of a gas.
- Use the ideal gas law in stoichiometry problems involving gases that are not at STP.
- Explain the conditions under which real gases are most ideal or least ideal.
Lesson Vocabulary
- ideal gas constant
- ideal gas law
- real gas
Check Your Understanding
Recalling Prior Knowledge
- What assumptions from the kinetic-molecular theory of gases are not capable of being precisely followed?
- How is molar volume used in stoichiometry and gas density calculations?
The combined gas law is useful for analyzing situations where a gas at a certain initial set of conditions is changed
to a new set of conditions. In this lesson, you are introduced to the ideal gas law, which is useful for studying a
quantity of gas under any given conditions of temperature and pressure.
Ideal Gas Law
A number of relationships between the four variables that are used to describe gases—P, V, T, and n—have been
established with the gas laws from the previous lesson. The combined gas law shows that the pressure of a gas is
inversely proportional to volume and directly proportional to temperature. Avogadro’s Law shows that volume or
pressure is directly proportional to the number of moles of gas. Putting these together leaves us with the following
equation.
P 1 ×V 1
T 1 ×n 1=
P 2 ×V 2
T 2 ×n 2