# The Combined Gas Law and Ideal Gas Law

When studying the properties of gases, you need to know the relationships between the variables of volume *(V)*, pressure *(P)*, Kelvin temperature *(T)*, and the amount in moles *(n) *so that you can calculate missing information (*P, V, T,* or *n*) and solve reaction stoichiometry problems. Although the pairs of variables have individual relationships, the two most important and useful gas laws are the *combined gas law* and the* ideal gas law:*

Combined gas law |
(P_{1}V_{1})/T_{1}= ( P_{2}V_{2})/T_{2} |
(T must be in Kelvin) |

Ideal gas law |
PV = nRT |
(R = 0.0821 L atm/K.mol) |