1) The ratio of the rates of diffusion of two gases x and sulphur (IV) oxide (SO₂) is 2:3 respectively, calculate the molecular mass of gas x given that (S=32.0,O=16.0)
Solution
Step I
Graham's Law of diffusion
Rate of diffusion of gas x⁄rate of diffusion of SO₂=
    √Molecular mass SO₂
    Molecular mass x

Step II
Get the molecylar mass of SO₂.
Sulphur has atomic mass of 32 and Oxygen is 16 and since they are 2 Oxygen atoms
you multiply the atomic mass of O by 2 to be 16x2=32 then add with 32 for S to make 64.
Step III