Question

A gas mixture contains 50% moles of He and 50% moles of CH₄. What is the percentage by mass of methane in the mixture?

Answer 1

Volume% of gas =mole % of gas (At constant temperature and pressure )

So mole % of He and CH4 will be 50% each .

Lets assume initially both had. x mole each

Mass of x mole He =4 x gram

Mass of x mole of CH4 = 16 x grams

Total weight 20 x grams

% He (by weight ) = (4 x/20 x )*100 =20%

% CH4 (by weight ) =(16 x/20 x)*100 =80%