Help with Graham's law

Question

What is the formula weight of a gaseous element if at room temperature it effuses though a

pinhole 2.16 times as rapidly as Xenon? Which element is it?

Answer 1

Graham's Law states rate gas 1/rate gas 2 = √MW gas 2/√MW gas 1

Xenon has an atomic mass = 131

Let's assume that it takes Xe 1 sec to effuse through the pinhole, then the unknown would effuse in 1/2.16 sec = 0.463 sec (2.16 times as rapidly)

0.463 = sqrt x / sqrt 131

sqrt x = 5.299

x = 28

Unknown gas is likely to be Nitrogen (N₂)