MHS AP Chemistry
Liquid Separations

Purpose:  To determine the identity of an unknown liquid mixed with n-decyl alcohol, based on boiling point and density.  Also, you will determine the mass percentage of the unknown in the original solution.

Procedure:  Using the organic chemistry kits supplied, set up a distillation apparatus as shown in chapter 1 of your textbook (also on this sheet).  Be very careful to make sure all seals are tight.  Use silicone sealant to prevent freeze-up.  Use a water bath between the heat source and the flask for more gentle heating.  Drain the vent nozzle into the sink.

Obtain a sample (about 50 mL) of the solution to analyze.  Record the mass of this sample as precisely as possible.  Also, record the identity of the solvent. Place ALL of this sample in your boiling flask.

Start the cooling water gently flowing through the condenser jacket, and turn on the hot plate.  Heat the unknown gently until it is boiling.  Record the boiling temperature.  Continue heating until the liquid stops boiling.

Record the mass of the liquid remaining in the boiling flask.  Record the mass and volume of the liquid condensed in the collection flask.
Calculations/Analysis:  Show the following data/results, numbered and in order:
  1. Initial mass of unknown mixture.
  2. Boiling temperature of the unknown component.
  3. Density and BP of the solvent
  4. Mass of solvent remaining behind after boiling.
  5. Mass of unknown recovered in collection flask.
  6. Total mass of liquids after boiling.
  7. Percent of initial total mass recovered.
  8. Mass % of unknown in original solution.
  9. Volume of liquid unknown condensed.
  10. Density of unknown.
  11. Identity of unknown.
  12. What error might result if the cooling water flow rate was too low?
  13. Why is there still liquid left when the solution stops boiling?


[Syllabus 4][MHS AP Chem page]