problem solution

Question

A sample of neon effuses from a container in 74 seconds. The same amount of an unknown noble gas requires 151 seconds.Identify the gas

Answer 1

Graham's Law of Effusion:

rate gas1/rate gas2 = sqrt MW gas2/sqrt MW gas1

151/74 = √x/√20

2.04 = √x/4.47

x = 83 = Krypton