Helium is found to diffuse two times faster than X. What is the molar mass of X?

1 answer

mm stands for molar mass
Let's say X diffuses at 5 mL/min. You can make up any number you want.
Then He diffuses at 10 mL/min since it is 2 times faster.
(rate He/rate X) = sqrt (mm X/mm He)
10/5 = sqrt (mm X/4)
mm X = ?