Q.
A mixture of methane and ethene in a molar ratio of x:y has an average molecular mass of 20u . The mean molar mass when they are mixed in the molar ratio of y:x will be -
Mol. wt. of CH4=16
Mol. wt. of C2H4=28 ∴20=x+y16x+28y
or 16x+28y=20x+20y
or 4x=8y
or x=2y
In the gaseous mixture when the mole ratio of CH4 and C2H4 is y:x
then avg.mol.wt=x+y16y+28x=3y16y+56y =3y72y=24u