Answer to Question #83483 in Molecular Physics | Thermodynamics for Shoukat Ali Shah

Question

If a valve is opened to let out enough air to bring the pressure back down to its original value, what percentage of the molecules escape?

Answer 1

P1*V1 = P2*V2 - Boyle's law

This is an inverse relationship between pressure and volume so if you compress the container and reduce the volume, pressure will go up.

Logic: compression reduces spaces between gas molecules and thus they collide more and more collisions create more pressure.

Use PV=nRT=NkT. You can see directly that the pressure depends on the number of molecules. To decrease the pressure ten-fold, back to its original value, in a fixed volume, 90 % of the molecules must escape, leaving one-tenth of the original number of molecules behind creating one-tenths of the original pressure.