moles of CH4 effused in the same time as Ar gas

Question

over a 14.5 minute period 4.17e-3 moles of Ar gas (molar mass=39.95 g/mol) effuses from a container. how many moles of CH4 gas (molar mass=16.04 g/mol) could effuse from the same container in the same period of time under the same conditions?

Answer 1

Use Graham's Law of Effusion:

rate gas₁/rate gas2 = √MW gas₂/√MW gas₁

So, rate of effusion is inversely proportional to the square root of the molar mass

For Ar, √39.95 = 6.32

For CH_4, √16.04 = 4.00

6.32/4.00 = 1.58

So, CH₄ will effuse 1.58 times faster than Ar (the lower MW effuses faster)

Moles of CH₄ effusing = 1.58 x 4.17x10^-3 = 6.59x10^-3 moles over the same 14.5 minute period.