A space capsule is filled with neon gas at 1.00 atm and 290 K. The gas effuses through a pin hole into outer space at such a rate that pressure drops by 0.30 torr per second.
(a) If the capsule is filled with ammonia at the same temperature and pressure, what would be rate of pressure drop?
(b) If the capsule is filled with 30.0 mol% helium, 20.0 mol% oxygen and 50.0 mol% nitrogen at a total pressure of 1.0 atm and a temperature of 290 K, what would be the corresponding rate of pressure drop?

Explanation

(a) The rate of pressure drop is directly proportional to rate of effusion.
`(r_(Ne))/(r_(NH_(3))) = sqrt((M_(NH_(3)))/(M_(Ne))) = sqrt((17.0)/(20)) = 0.92`
`r_(NH_(3)) = (r_(Ne))/(0.92) = (0.30)/(0.92) = 0.326` torr/second
(b) The average molecular mass of the gaseous mixture is
`0.3 xx 4 + 0.2 xx 32 + 0.5 xx 28 = 21.6`
Rate of drop of pressure `= sqrt((20)/(21.6)) xx 0.30`
`= 0.29` torr/second