Combined Gas Law

Rearranging the ideal gas equation $PV = nRT$ gives $\frac{PV}{T} = nR$, and since $n$ and $R$ are both constant for a fixed amount of a particular gas, $\frac{PV}{T}$ itself must be constant. So if the same fixed amount of gas is compared in two different states, an initial state ($P_1, V_1, T_1$) and a final state ($P_2, V_2, T_2$), then $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$. This relationship is called the combined gas law, because it folds Boyle's law, Charles's law and Gay-Lussac's law into one single expression -- if any two of pressure, volume and temperature change simultaneously for the same fixed quantity of gas, the combined gas …