Question

180ml of a hydrocarbon diffuses through a porous membrane in 15 minutes while 120ml of SO2 under similar conditions diffuses in 20 minutes. What is the molecular mass of hydrocarbon? and how

Answer 1

$180 + 120 = 300 \\ 15 - 20 = - 5$
$- 15 + 300 = 285$

Answer 2

Answer

According to Graham's law of diffusion:

r1r2=√M2√M1

where

r = rate of diffusion

M = Molecular mass

r = Volume effusedtime=Vt

So,

r1r2 = √M2√M1⇒V1/t1V2/t2 = √M2√M1

⇒180/15120/20=√64√M1 (Molecular mass of SO2 = 64 g/mol)

⇒180×20/120×15 = 8/√M1 8×120×15180×20⇒√M1

On squaring both sides⇒M1 = 16

So, molecular mass of the hydrocarbon = 16 g/mol