Under identical conditions, separate samples of O2 and an unknown gas were allowed to effuse through identical membranes simultaneously. After a certain amount of time, it was found that 7.88 mL of O2 had passed through the membrane, but only 3.69 mL of of the unknown gas had passed through. What is the molar mass of the unknown gas

146.5g/mol

Explanation:

The volume of  gas effused is directly proportional to the square root of its relative molecular mass.

Let the volume of oxygen gas be V1

Let the volume of the unknown gas be V2

Let the molar mass of oxygen be M1

Let the molar mass of the unknown gas be M2

V1/V2 =√M2/M1

7.88/3.69 = √M2/32

2.14 = √M2/32

(2.14)^2 = M2/32

4.58 = M2/32

M2 = 32*4.58

M2 = 146.5g/mol