calculating average molecular weight of gases

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Calculate the average molecular weight of gases for following cases: (1) Consider the gas has a molar composition of 30% nitrogen, 25% oxygen, 25% helium and the balance is methane Calculate the average molecular weight of this gas. (15 marks) (2) Consider the gas has composition by mass of 25% nitrogen, 238 oxygen, 32% helium and the balance is carbon dioxide. Calculate the average molecular weight of this gas. (15 marks) (3) Why is it important to estimate the average molecular weight of gas mixtures in the chemical process industry? (10 marks) Note: Show your solution in detail and write the answer in your own words