Question

16. A mixture contains 80% of unknown gas and 20% of oxygen. When 100cc of pure oxygen were
diffused through a porous membrane, 84.51 cc of the gas mixture were diffused through the same
membrane, at the same time under identical conditions. Find the molecular mass of unknown gas

Answer 1

Answer:

A gaseous mixture of O

2

and X containing 20 % of X, diffuses through a small hole in 234 s while pure O

2

take 224 s to diffuse through the same hole. The molecular mass of the mixture is:

Explanation:

Correct option is

A

34.9

The rate of diffusion is the ratio of quantity diffused to time.

The rate of diffusion is inversely proportional to square root of molecular mass. When same quantity of two gases diffuses,

t

O2

t

mixture

=

M

O2

M

mixture

224

234

=

32

M

mixture

1.0446=

32

M

mixture

1.091=

32

M

mixture

M

mixture

=34.9 g/mol

Hence, the correct option is A