|The combined gas law is not a new law but a combination of
and Charles' laws, hence the name the
combined gas law.
In short, this combined gas law is used when it is difficult to keep
the temperature or pressure constant. In many experiments with
keeping either the pressure or temperature constant is not even
The combined gas law equation is:
|The temperature must be in kelvins, but the pressure and
can be in any units as long as they are used consistently; that is,
pressure values must be in the same pressure units and both volume
must be in the same volume units.
|This law also contains a third law that is implied but not
stated. The pressure-temperature law was discovered by Jacques
and Joseph Gay-Lussac (1778-1850), a French scientist. It was not
given a name because it is easily obtained by using Boyle's and
Laws properly, however, it is given below for your enjoyment. If
the volume of a gas is fixed during an experiment then the
and temperature vary in a specific way.
|This law, known as Gay-Lussac's Law
P1T2 = P2T1