In terms of gas mixtures, what does the mole fraction represent?

The mole fraction is a fundamental concept in the study of gas mixtures that quantifies the proportion of a particular component in the mixture relative to the total number of moles present. Specifically, it is defined as the ratio of the number of moles of a single gas to the total number of moles of all gases in the mixture. This measurement provides insight into the composition of the mixture, allowing for calculations involving partial pressures and other properties that depend on the presence and behavior of various gases.

For example, if there are 2 moles of gas A and 3 moles of gas B in a mixture, the total number of moles is 5. The mole fraction of gas A would be calculated as 2 moles of A divided by 5 total moles, yielding a mole fraction of 0.4. This underlies the importance of understanding mole fractions in both theoretical and practical applications, such as in the Ideal Gas Law and Dalton's Law of Partial Pressures. Thus, the correct answer accurately reflects the definition of mole fraction and its role in gas mixtures.