What is the molar mass of a gas if it takes 7.3 min to effuse through a small hole and 6.1 min for the same amount of N₂ to effuse through the same hole?

Question

Quizplus · Accepted Answer

The molar mass of the gas can be determined using Graham's law of effusion, which states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass. Given the times for effusion, we can set up the ratio of the square roots of the molar masses of the unknown gas and N₂ (which is sulfur hexafluoride, SF6, with a molar mass of approximately 146 g/mol). The equation based on Graham's law is: (time for unknown gas / time for SF6) = sqrt(molar mass of SF6 / molar mass of unknown gas). Plugging in the given times (7.3 min for the unknown gas and 6.1 min for SF6) and solving for the molar mass of the unknown gas gives a value close to 40 g/mol.

What Is the Molar Mass of a Gas If It