Rate of Effusion and Molecular Mass?

Question

1.177×10-4 mol of an unidentified gaseous substance effuses through a tiny hole in 77.2 s.
Under identical conditions, 1.638×10-4 mol of argon gas takes 82.3 s to effuse.

What is the molar mass of the unidentified substance (in g/mol)?

___________ g/mol

The percentage C by mass in the above unidentified substance is 53.0%. It may also contain H and/or O, but no other element.
What is the molecular formula of the substance?
(In typing this formula use the convention of C first, H second and O last. For example, C6H8O2 would be C6H8O2.)

Under identical conditions, how many moles of allene (C3H4) gas would effuse in 82.1 s?
________ mol

Answer 1

Look up, and use, Graham's Law of Diffusion (Effusion).