Question

The mean molecular mass of a mixture of methane and ethene is in the molar ratio of x : y is found to be 20. What will be the mean molecular mass if the molar ratio of the gases is reversed ?

Answer 1

Molar ratio of methane : ethene = x:y

Mean molecular mass of the mixture = 16x + 28y / x+y

Now,

16x + 28y / x+y = 20

On solving,

x/y = 2/1

On reversing y/x = 1/2

so, 1:2 = (16 x1 + 28x 2)/3 = 24