chemistry help please

Question

O2 gas travels at a rate of 25 m/s. Calculate the molecular mass of an unknown gas travelling at a rate of 15 m/s.

Answer 1

Graham's Law of Effusion:

rate gas 1/rate gas 2 = sqrt MW gas2/sqrt MW gas 1

25/15 = sqrt x/ sqrt 32

1.667 = sqrt x/5.66

sqrt x = 9.43

x = 88.9 = molecular mass of unknown gas