Question

It takes 200. seconds for a sample of carbon dioxide to effuse through a porous plug and 280. seconds for the same volume of an unknown gas to effuse under the same conditions. What is the molar mass of the unknown gas? Enter your answer to 3 significant figures.

Answer 1

Choose a convenient volume such as 1 L. Then rate CO2 = 1L/200 s = ?
rate unknown = 1L/280 s =
(rate CO2/rate unk) = sqrt(MMunk/MMCO2)
MM = molar mass. Solve for MM unk.l

Answer 2

39.7