Question

A flask containing `12 g` of a gas relative molecular mass `120 at` a pressure of `100 atm` was evacuated by means of a pump until the pressure was `0.01 atm`. Which of the following in the best estimate of the number of molecules left in the flask `(N_(0)=6xx10^(23)mol^(-1))`?
A. `6xx10^(9)`
B. `6xx10^(18)`
C. `6xx10^(17)`
D. `6xx10^(13)`

Answer 1

`P_(1)V_(1)=n_(1)RT_(1)`
`P_(2)V_(2)=n_(2)RT_(2)`
`(n_(2))/(n_(1))=(P_(2))/(P_(1))`
`n_(2)=0.1xx(0.01)/(100)=10^(-5) mol= 6xx10^(18)` molecules