Calculate Resulting Pressure of Mixed Gases in 12L Vessel

[oceanflavored]

Homework Statement

What is the resulting pressure when the quantities of gases listed below
are mixed and placed in a 12 L vessel at constant temperature?
4.0 L Ne measured @ 2.0 atm
2.0 L He measured @ 3.0 atm
2.0 L Ar measured @ 5.0 atm

Homework Equations

P1V1=P2V2

The Attempt at a Solution

the answer is 2.0 atm.and i have no clue how they figured that out.
because i tried to do it by the above equation. and that definitely did not work out.and then i tried adding up the initial volumes:8 L and the initial temperatures:10 atm.and that didn't work either.so basically;i need helpp.
and hopefully.before tuesday morning.because that's when my ap chem test is. which is why you see me here posting all these questions.

thanks a lot physicsforum people.you guys seriously save my life these days

 

[lalbatros]

One method: calculate the number of mole of each component, add up, use the perfect gas law for the desired volume.

Second method: convert all components as volumes for 1 atm, add up the volumes still at 1 atm, compress to the desired volume. (this method is the same as the previous one, but moles are replaced by "standard volume").