Gas+Mixtures+and+Partial+Pressures

Gas Mixtures and Partial Pressures
Gas mixtures (a combination of two or more gases) follow **Dalton’s Law of Partial Pressures**. In gas mixtures, each individual gas has a pressure that it would have if it occupied the space by itself at the same temperature. This pressure is called a gas mixture’s **partial pressure**. The total pressure of a gas mixture can be found by adding up the partial pressures of the gases present in the mixture. The equation for the total pressure of a gas mixture is:



Dalton’s Law shows that each gas in a mixture behaves on its own and maintains its own individual characteristics. Because all of the gases in a gas mixture have the same temperature and volume, the ideal-gas equation (PV=nRT) can also be used to find the total pressure of a gas mixture. The ideal-gas equation uses the number of moles instead of the total of the partial pressures to find the total pressure.



Mole Fractions
Mole fractions are used to relate the amount of a gas in a mixture to the gas' partial pressure. In the equation to find the partial pressure, X is the ratio of number of moles in the individual gas to the total number of moles in the mixture.



Sources: http://en.wikipedia.org/wiki/Partial_pressure //Chemistry: The Central Science//