Question

000 atm of dry nitrogen, placed in a container having a pinhole opening in its side, leaks from the container 3.55 times faster than does 1.000 atm of an unknown gas placed in this same apparatus. which of these species could be the unknown gas?

Answer 1

We will assume that the question is discussing 1.000 atm of N₂ initially. The question is discussing diffusion rates of two gases and asks us to identify the species. We can use Graham's Law to attempt this problem with the following formula:

Rate₁/Rate₂ = sqrt(M₂/M₁)

We are told that the N₂ is 3.55 times as fast as the unknown species, so rate 1 = 3.55 and rate 2 = 1. We know the molecular weight of N₂ as 28 g/mol. Now we can use the equation above to solve for the molecular weight of the unknown, M₂:

3.55/1 = sqrt(M2/28)
(3.55)² = M₂/28
M₂ = 28 (3.55)₂
M₂ = 353 g/mol

The unknown compound has a molecular mass of roughly 353 g/mol and this is very close to the molecular mass of UF₆ which is 352.02 g/mol. Therefore, it is likely that the unknown gas is UF₆.