Gas Laws

The Gas State

Boyle’s Law

Charles Law

Avogadro’s Law(Hypothesis)

Gay Lussac’s Law

Pressure Temperature Law

Dalton’s Laws or Partial Pressures


The kinetic-molecular theory of gases can be stated as four postulates:

A gas consists of molecules in constant random motion.

Gas molecules influence each other only by collision; they exert no other forces on each other.

All collisions between gas molecules are perfectly elastic; all kinetic energy is conserved.

The volume actually occupied by the molecules of a gas is negligibly small; the vast majority of the volume of the gas is empty space through which the gas molecules are moving.

Standard state:

STP Standard temperature and pressure
Temperature = 0o C  or 273.14 K
Pressure = 101.325 kPa
Volume = 22.4 L

SATP Standard ambient temperature and pressure
Temperature =  25oC or 298 K
Pressure = 100 kPa
Volume = 24.8 L

Universal Gas Constant  R =  8.314  J/mol K or 8.314  kPa dm3/mol K

Commonly used units of pressure

Atmosphere      atm.

Kilopascal         kPa                   Conversion unit 1atm/101.325 kPa

Toricelli             torr.                 Conversion unit 1atm / 760 torr

Millimeter       mm                  Conversion unit 1 atm / 760 mm

1 atm. = 101.325 kPa = 760 torr   = 760 mm



Celsius and Kelvin

Conversion:  Kelvin = degrees Celsius + 273

K = oC + 273

In all SI metric calculations use only  Kelvin values.