Posted by Warren on .
My AP Chem class did a lab for determing the molar mass of a volatile liquid by vapor density. There are a few calculations that I can't seem to get:
1.) The moles of air displaced by the volatile liquid vapor (at RT)
2.) The molar mass of air (calculated)
3.) Mass of air displaced by the volatile liquid vapor
What I know already is:
1.) The aparent mass of vapor that occupied the flask at the boiling water temperature
2.) the volume of the flask
3.) Moles of gas occuping the flask at the BP of water.
4.) estimated molar mass of the unknown liquid
What we did is fashion an apparatus using copper wire and aluminum foil to an Erlenmyer Flask and injected 3-4 mL of this unknown liquid and then put the flask in a beaker with water on a hot plate to evaporate the liquid and then determine the mass of the flask, apparatus, AND vapor. Thanks in advance.
I'm sorry but there just isn't enough information here for me to be helpful. Nothing about the kind of apparatus, is the Cu wire and Al foil inside or outside the flask and do they react, nothing about masses (how much of what), etc. The volume of a flask is determined sometimes by weighing the empty flask, filling with water and reweighing, then calculating the volume from the density of water.