During an diffusion experiment, it took 75 seconds for a certain number of moles of an unknown gas
to pass through a tiny hole. under the same conditions, the same number of moles of oxygen gas
passed through the hole in 30 seconds. what is the molar mass of the unknown gas?

200 g/mol is the molar mass of the unknown gas.

Explanation:

Effusion is defined as volume of gas dispersed in a given interval of a time.

Number of moles of gas are directly proportional to the volume occupied by the gas.

(at constant temperature and pressure)

If n moles of unknown gas occupies V volume then n moles of oxygen will occupy:

The n moles of unknown gas pass through a tiny hole in 75 seconds.The effusion rate is give as:

The n moles of oxygen gas pass through a tiny hole in 30 seconds.The effusion rate is give as:

According to Graham law: the effusion rate is inversely proportional to the square root of molar mass of the gas.

200 g/mol is the molar mass of the unknown gas.