Gas law

Ideal Gas Law Glossary

  • Absolute Pressure: Actual pressure of gas inside a container, no reference to outside pressure.

  • Gauge Pressure: Difference between absolute pressure and atmospheric pressure.

Key Gas Laws

  • Boyle’s Law: P1 V1 = P2 V2 (Pressure and volume at different states)

  • Charles’s Law: \frac{V1}{T1} = \frac{V2}{T2} (Volume and temperature relation)

  • Avogadro’s Law: \frac{V1}{n1} = \frac{V2}{n2} (Volume and number of moles)

Ideal Gas Law Formula

  • PV = nRT

    • P: Pressure

    • V: Volume

    • n: Number of moles

    • R: Ideal gas constant = 8.314 L kPa mol K or L atm mol K

    • T: Temperature (must be in Kelvin)

Using the Ideal Gas Law

  • Calculate unknown if three variables are known: Rearrangement gives n = \frac{PV}{RT}

  • Ensure units match those of the ideal gas constant:

    • Volume: L

    • Pressure: atm or kPa

    • Temperature: K

Application Examples

  1. Pressure and moles calculation from a gas sample given values.

  2. Conversion of temperature from Celsius to Kelvin: K = °C + 273.15

  3. Calculation of gauge pressure when given absolute and atmospheric pressures.

Mixtures of Gases

  • Each gas in a mixture can be treated individually.

  • Total pressure is the sum of partial pressures: P{total} = P1 + P2 + … + Pn

Important Rearrangements of the Ideal Gas Law

  • To solve for pressure (P): P = \frac{nRT}{V}

  • To solve for volume (V): V = \frac{nRT}{P}

  • To solve for number of moles (n): n = \frac{PV}{RT}

  • To solve for temperature (T): T = \frac{PV}{nR}