Ideal gas law

Definition

The Ideal Gas Law is a fundamental equation in physics that relates the pressure, volume, temperature, and number of moles of an ideal gas. It is expressed as $PV = nRT$, where $P$ is pressure, $V$ is volume, $n$ is the number of moles, $R$ is the universal gas constant, and $T$ is temperature.

5 Must Know Facts For Your Next Test

1. The Ideal Gas Law combines Boyle's Law, Charles's Law, and Avogadro's Law.
2. $R$, the universal gas constant, has a value of 8.314 J/(mol·K).
3. Ideal gases are hypothetical; real gases approximate ideal behavior under low pressure and high temperature.
4. The units for pressure ($P$) commonly used are atmospheres (atm), pascals (Pa), or torr.
5. Temperature ($T$) must always be in Kelvin when using the Ideal Gas Law.

Review Questions

• What are the variables in the Ideal Gas Law equation?
• How does an increase in temperature affect the volume of an ideal gas if pressure and moles are held constant?
• What unit must temperature be in when using the Ideal Gas Law?

Related terms

Boyle's Law:

States that for a fixed amount of gas at constant temperature, the volume is inversely proportional to the pressure.

Charles's Law: States that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature.

Avogadro's Law:

$V \propto n$, meaning that at constant temperature and pressure, equal volumes of gases contain an equal number of molecules.