Record the information that you know about the gases in the container. Chemistry problems that involve calculating the ratio of pressures in a container will provide you with the total pressure and the number of moles of each gas. For example, the problem may tell you that the total pressure in the container is 4.00 atmospheres and that there are 2.00 moles of neon, 1.00 mole of argon and 1.75 moles of xenon in the container.
Find the mole ratios of each of the gases. To find the mole ratios of the gases, find the total number of moles, and then divide number of moles of each gas by the total amount. For example, the total amount of moles of the gases is 2.00 plus 1.00 plus 1.75, a total of 4.75 moles. To find the mole fraction of neon, divide 2.00 moles by 4.75 moles, giving you an answer of 0.421. The mole fraction of argon is 0.211, while the mole fraction of xenon is 0.368.
Solve the equation for the partial pressure. The partial pressure of the gas is equal to the mole fraction of the gas times the total pressure of all the gases in the container. For example, the partial pressure of neon is 0.421 times 4.00, for a result of 1.68 atm. The partial pressure of argon is 0.211 times 4.00, or 0.844 atm. The partial pressure of xenon is .368 multiplied by 4.00, or 1.47 atm.