AP Chemistry Gas Laws?

  • Thread starter Thread starter Klaus
  • Start date Start date
K

Klaus

Guest
2.00 g of an unknown volatile liquid was placed in a flask with a total volume of 265.0 mL. The cover of the flask has only a pinhole, which allows the internal pressure to equilibrate with the outside pressure. The temperature was raised to 100.00C by placing the flask in a constant temperature water bath. At this temperature, it was found that only 0.581 g of the liquid substance remained in the flask. A barometer in the lab showed the pressure to be 752 mm Hg. What's the molar mass of the unknown liquid?
 
PV = nRT

n = m / M (mass / molecular weight)

PVM = mRT

M = mRT / PV

m = .581 g
V = .265L
P = 752 torr
T = 100 C = 373 K
R = .08206 L-atm / K-mol

you'll need to do some conversions, but that should get you there.
 
Back
Top