w WAL ons [Hint: First determine the average molecular mass and then number of moles of helium and oxygen. ad be Moles of helium = 0.665; Moles of oxygen = 0.335 Ti t o Mass per cent of helium 4* 0.663 2008 S 4*0.665 + 32 x 0.335 * 100 = 19.88) (20. A sample of natural gas is 85.2% methane and 14.8% ethane by mass. What is the density of this mixture at 18°C and 748 mm Hg? (Ans. 0.74 g L-') V uler mose of mischinen us . 1 1.0821 x 273 = 29.137 01 ... (ii) 28n; +32m 51 war a mb m+n2 -= 29.137 or 2-= 1.137 s lo mor 08132 adwo rtendi +12 m m =0.28 = mole fraction of oxygen Taisin Partial pressure of Oz =0.28 x 1 = 0.28 atm) 27. At a definite pressure and temperature 100 ml hydrogen diffused in 20 minute. How long w ng as mL of oxygen take to diffuse under similar istions?d B ni bosimizi tanda di fan (Ans. 32 minute to 28. At a given tem t of air ter cha (An (Hind Low long will 40 Similar condi- Inside pressure