Question

If the initial pressures of the H2 and N2 in the flasks in the figure below were instead 350. torr and 160. torr, respectively, what would be the final pressure after the stopcock is opened?
Left side of stopcock= 2.00L H2
Right side of stopcock= 1.00L N2

Answer 1

I would use PV = nRT and solve for n for H2 flask. So the same for N2 flask. You have no T listed but you can make up a T (and keep it the same throughout). Then add n1 + n2 and use PV = nRT again with total mols and total volume, solve for P.

A shorter route is to use
P1V1 = P2V2 and convert pH2 from 2L @ 350 mm to 3L at ? P.
Do the same for converting pN2 from 1L @ 160 mm to 3L @ ?P. Then add pH2 + pN2 = Ptotal. You will get the same answer either way.