The density of the vapour of a substance at 1atm pressure and 500k is 0.36kgm−3. The vapour effuse through a small hole at a rate of 1.33 times faster than oxygen under the same condition.
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Solution
Using Graham's law of diffusion,
r1r2=√M2M1⇒1.331=√32gmol−1M1⇒M1=18.09gmol−1
The molar volume of the vapour, Vm=M1α
=18.9gmol−10.36Kgm−3
=18.09gmol−10.36gdm−3
=50.25dm3mol−1
The compressibilty factor, Z=Vm,realVm,ideal=Vm,realRT/α
=101.325KPa×50.25dm3mol−18.314JK−1mol−1×500K
=1.22
Since Z>1 the repulsive forces dominate among the gaseous molecules.