What is the mole fraction of oxygen in a gas mixture that is 40.0% oxygen and 60.0% nitrogen by volume?
A)0.632
B)0.368
C)0.400
D)0.600

Question

Quizplus · Accepted Answer

The mole fraction of a component in a mixture is the ratio of the number of moles of that component to the total number of moles of all components in the mixture. For gases, if the mixture is ideal, the mole fraction is also the volume fraction because of Avogadro's law (equal volumes of gases, at the same temperature and pressure, contain the same number of molecules). Therefore, the mole fraction of oxygen, which is 40.0% by volume, is simply 0.400. However, the correct interpretation of the question leads to the realization that the mole fraction is directly given by the percentage (divided by 100), thus the correct answer is 0.400, which is not listed as an option based on the initial response. The mistake was in the initial interpretation of the choices provided. The correct answer should have been identified as C) 0.400, reflecting the direct conversion of the volume percentage to a fraction.

What Is the Mole Fraction of Oxygen in a Gas