Chemistry - Mole Concept Question with Solution | TestHub

According to Avogadro's law, equal numbers of moles of gases occupy the same volume under identical conditions of temperature and pressure. Even if we have a mixture of non-reacting gases, Avogadro's law is still obeyed by assuming the mixture as a new gas.

Now, let us assume air consists of 80% by volume of Nitrogen (N₂) and 20% by volume of Oxygen (O₂). If air is taken at STP, then 1 mole of air would occupy 22.4 L. One mole of air would contain 0.8 mol of N₂ and 0.2 mol of O₂, hence the mole fractions of N₂ and O₂ are given by $X_{N_2}=0.8$ and $X_{O_2}=0.2$.