In an effusion experiment it required 40 s for a certain number of moles of a gas of unknown molar mass to pass through a small orifice into a vacuum. Under the same conditions 16 s were required for the same number of moles of O2 to effuse. What is the molar mass of the unknown gas?

The molar mass of the unknown gas is 200 g/mol

calculation

let the unknown gas be represented by Y and molar mass be represented by MM

The molar mass of Y is therefore calculated using

= (time of Y / time of O2) = √ (MM of Y / MM of O2 formula.

where MM of y = ?

MM of O2 = 32 g/mol

time of Y = 40 s

time of O2 = 16 s

40/16 = √ (MM of Y / 32)

2.5=√MM of Y/32

square both side to remove the √ sign

6.25 = MM of Y/32

multiply both side by 32

MM of Y is therefore = 200 g / mol