Three bulbs are connected by tubing, and the tubing is evacuated. The volume of the tubing is 32.0 mL. The first bulb has a volume of 78.0 mL and contains 2.72 atm of argon, the second bulb has a volume of 250 mL and contains 2.83 atm of neon, and the third bulb has a volume of 37.0 mL and contains 8.24 atm of hydrogen. If the stopcocks (valves) that isolate all three bulbs are opened, what is the final pressure of the whole system in atm?

Question

So I know that you have to use PV=PV, but how would you do it with three different bulbs? I mean, how would you get the volume of the whole system?

The following procedure provides a crude method of determining the molar mass of a volatile liquid. A liquid of mass 0.0171 g is introduced into a syringe and the end is capped (sealed). The syringe is transferred to a temperature bath maintained at 62.7 oC, and the liquid vaporizes. As the liquid vaporizes the plunger is pushed out. At equilibrium, the plunger reads 6.81 mL of gas. Atmospheric pressure is 740. mmHg. What is the approximate molar mass of the compound (in g/mol)?

Okay for this one I would us V/T=V/T, but why do they mention atmospheric pressure/how does it play into solving the problem?

Thanks in advance!

Answer 1

For #1, the volume of the entire system is volume bulb 1 + volume bulb 2 + volume bulb 3 + 32 mL (for the tubing).

Answer 2

To go further on #1, I would use PV = nRT and convert those volumes and pressures to mols = n. The add all the moles together and the volumes together and use PV = nRT to solve for P. You don't have a T but you can make up a T and keep it constant.