A flask containing 12 g of a gas of relative molecular mass 120 at a pressure of 100 atm was evacuated by means of a pump unitl the pressure was 0.01 atm at the same temperature. What is the approximate number of molecules left in the flask ?

A flask containing 12 g of a gas of relative molecular mass 120 at a p

1.	A flask containing 12 g of a gas of relative molecular mass 120 at a pressure of 100 atm was evacuated by means of a pump unitl the pressure was 0.01 atm at the same temperature. What is the approximate number of molecules left in the flask ?
Answer» <P> Solution :Initially,`n_(1)=(12)/(120)` mole=0.1 mole, `P_(1)`=100 atm, `T_(1)`=T, `V_(1)`=V After evacuation,`n_(2)`=? `P_(2)=0.01`atm, `T_(2)=T, V_(2)=V` ApplyingPV=nRT As V and T an constant, `(P_(1))/(P_(2))=(n_(1))/(n_(2))` `(100)/(0.01)=(0.1)/(n_(2))"or"n_(2)=(0.1xx0.01)/(100)=(10^(-1)xx10^(-2))/(10^(2))=10^(-5)` mole No. of MOLECULES left `=(10^(-5))(6.02xx10^(23))=6.02xx10^(18)`