# Fractional Distillation Calculations

1. Mar 21, 2012

### boredbluejay

1. The problem statement, all variables and given/known data

4-bromotoluene was synthesized and purified by distillation. There are 5ml of the crude product. A fractional distillation is being carried out in a 100ml round bottom flask. Assume that the volume of the column is 16ml. Determine the number of moles of 4-bromotoluene that will remain vaporized and cannot be collected. What will the volume of the condensed vapor be?

2. Relevant equations

PV=nRT
Total Pressure=χaPa+χbPb, where χis the mole fraction of a or b and P is the normal pressure of a or b.
bp of 4-bromotoluene is 184C
density=1.39g/ml
MW=171.13g/mol

3. The attempt at a solution

I know that we are trying to find n using PV=nRT. However, I'm not sure which values we plug in. Do I use V=16ml for the volume inside the column? Do I use the boiling point for T? Also, how do you find the pressure of the system? If P= the total pressure of the mixture, how would you find it if you don't know how much of the compound is made up of 4-bromotoluene and what the pressure of 4-bromotoluene is?

Thank you very much!