One mole of O2 and two moles of N2 are mixed to calculate the average molecular weight of the mixed gas

One mole of O2 and two moles of N2 are mixed to calculate the average molecular weight of the mixed gas

Average molecular weight = total mass / total material weight = (1 * 32 + 2 * 28) / (1 + 2) = 29.3
Answer: 29.3