A vessel of capacity 400cc and filled with chlorine under 80 cm is connected by a narrow tube and stop with another vessel of capacity 250cc filled with nitrogen under 100cm. What will be the pressure when the stop is opened???
There may be an easier way to do this but here is what I would do. BTW, I assume that 80 cm is 80 cm Hg pressure.
For vessel 1 use PV = nRT. You know P, V, R, (T is not given so just plug in 273 K). Solve for n1 = number of moles gas in vessel 1.
Do the same for vessel 2 and solve for n2. Then find the total moles or
ntotal = n1 + n2 and use PV = nRT where
Psystem when stop is open, v is total volume or v1 + v2, ntotal, and plug in what you've been using for T. Solve for Psystem.
Post your work if you get stuck.