Question
Sun May 22, 2011 By:

1 L of a gass is at a pressure of 10 to the power -6 mm of hg at 25 degree cesius.how many molecules are in the vessel?

Expert Reply
Mon June 06, 2011
THINGS GIVEN
 
PRESSURE=10-6mm of Hg
We know that 760mm of Hg=1 atm
 Therefore,10-6 mm of Hg=(10-6/760)atm=0.001316×10-6 atm
volume=1litre
R=0.0821
T=(273+25)K=298K
 
Therefore,if the gas is assumed to be an ideal gas,then PV=nRT
n=PV/RT=(0.001316×10-6)×1/(0.0821×298)=5.4×10-11 moles
now,1mol of gas has 6.023×1023 no. of molecules
therefore,5.4×10-11 mol has 32.5242×1012 molecules.
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