 There are two types of gas
equations. One is the class of equations describing a
what happens when a gas changes from one condition to
another. The second class of equations describe a single
state where NO changes occur.

Single state equations no
changes

Dalton's law

P_{total} =
P_{1}
+ P_{2}
+ P_{3}....

Universal gas law

PV = nRT

Gas density at STP, grams /
Liter

density = d = molar mass/ 22.4
L

Change of state equations Two
states or conditions exist, both an initial and final state

Boyle's law

P_{1}V_{1}
= P_{2}V_{2}

constant T and moles




Charle's law

V_{1}/T_{1}
= V_{2
}/T_{2}

constant P and moles




GayLussac's law

P_{1}/T_{1}
= P_{2
}/T_{2}

constant V and moles




Combined gas law

P_{1}V_{1}/T_{1}
= P_{2}V_{2
}/T_{2}

constant moles




Avogadro's law

n_{1}/V_{1}
= n_{2}/V_{2}

constant T and P

All these equations follow
assumptions of the kinetic molecular theory for
gases.

Standard temperature and
pressure, STP

From the preceding equations it should
be clear that gas properties change with temperature and
pressure. A standard reference condition has been defined so
comparisons of gases can be made. A reference standard
temperature and pressure, are set at STP,
273.16^{o}
Kelvin and 1 atmosphere pressure.

All gases at STP have the same molar
volume, 22.4 Liters. This naturally comes about when the
Ideal / Perfect Gas law is used to calculate volume for 1
mole at STP.

Dr. Walt
Volland, all rights reserved
19982005
