The rate of effusion of oxygen to an unknown gas is 0.935. what is the other gas?

N2

Explanation:

Rate of effusion is defined by Graham's Law:  

(Rate 1/Rate 2) = (sqrt (M2)/ sqrt (M1))

(Where M is the molar mass of each substance. )

Molar Mass of oxygen, O2, is 32 (M1).

Rate of effusion of O2 to an unknown gas is .935(Rate 1).  

Rate 2 is unknown so put 1.

Solve for x (M2).

.935/1 = sqrt x/ sqrt32

.935 x sqrt 32 = sqrt x

5.29 = sq rt x

5.29^2 = 27.975 = 28  

N2 has a molar mass of 28 so it is the correct gas.