Problem 15E

What is partial pressure? What is the relationship between the partial pressures of each gas in a sample and the total pressure of gas in the sample?

Solution 15E When different gases form a mixture, each of these gases exerts a certain amount of pressure. This hypothetical pressure exerted by an individual gas component of a mixture is called the partial pressure of that gas component. Partial pressure is a measure of thermodynamic activity of the gas’s molecules. When you get the sum of the partial pressures of the different gas components, you will be able to obtain the total pressure. The equation to get the total pressure of a gas mixture containing gases X, Y, and Z is shown below. Using the ideal gas equation, it can be said that there is direct proportionality between the number of moles of a gas and the partial pressure of the gas. This means the higher number of moles of a gas, the higher partial pressure relative to the total pressure will be expected. This can be easily described by using the mole fraction of the gas. The mole fraction of a gas is equal to the quotient of the partial pressure a gas and the total pressure of the gas mixture. Multiplying the mole fraction by the total pressure, one can obtain the partial pressure of the gas.