The ratio of rates
Graham's Law states that:
Rate of effusion
For two gases:
Use Grahams's law, which states that the rate of effusion of a gas is inversely proportional to the square root of molar mass.
This means that the rate of effusion of chlorine gas will be
Likewise, the rate of effusion of nitrogen gas will be
If you divide these two expressions, you'll get the ratio of effusion rates of chlorine and nitrogen
The numerical value of this ratio will be
Here is a video which shows how to solve a different problem using Graham's law.
Video from: Noel Pauller
Hope this helps!