Question

A sample of an unknown gas effuses in 11.2 min. an equal volume of h2 in the same apparatus at the same temperature and pressure effuses in 2.31 min. what is the molar mass of the unknown gas?

Answer 1

The time of effusion of a gas is directly proportional to the square root of the molar mass
Let the unknown gas to be represented by y
therefore;
Ty/TH2=sqrt(y/H2)
11.2min/2.31min=sqrt(y/2)
square both side to remove the square root sign
(11.2^2 / 2.31^2) =y/2
23.5=y/2
multiply both side by 2
y is therefore 47