Experiment 2: Fractional Distillation
Date: October 5, 2006
Khadijah Ali (100142747) and Navdeep Kaur (100158810)
Objective: To separate a mixture of methanol and water using fractional distillation (macroscale) and determine the % by mass (and volume) of methanol in the fractions using measured refractive index.
Chemical Structures:
 
Procedure:
Set up fractional distillation apparatus. In round bottom flask added 30 mL of unknown liquid and boiling chips. Used condenser with glass beads (on which the liquid would condense), thermometer, fractionating column etc. (See page 15 of Lab Manual for visual depiction).-
Distillated unknown methanol/water liquid, using Variac, while changing graduated cylinder when temperatures reached 68°C (Fraction 1), 97°C (Fraction 2) and 100°C (Fraction 3).
For detailed procedure, please refer to Lab Manual 2006 Edition, pages 18-19.
Observations:
Methanol/water mixture is colourless liquid.
Boiling stones are white solids.
There is production of vapour during distillation.
The liquids produced are also colourless.
Data:
Unknown #90
+++++++++++ % by mass methanol Refractive index Volume (mL)
Temperature
Original 32 % 1.3410 30 mL room
F1 99-100 % 1.3287 9.1 mL 68 °C
F2 24 % 1.3392 0.9 mL 97 °C
F3 < 6 % 1.3344 8.0 mL 99 °C
Calculations:
Original Mixture:
Sample volume = 30.0 mL
% by mass of methanol from refractive index = 32 %
Density of mixture (CRC) = 0.9482 g/mL
Mass of 30.0 mL sample = 30.0 mL x 0.9482 g/mL = 28.446 g
Mass of methanol in 30.0 mL of sample = 28.446 g x 0.32 = 9.103 g
Volume of methanol in sample = 9.103 g x 1 mL/0.791 g = 11.508 mL
Fraction 1:
Sample volume = 9.1 mL
% by mass of methanol from refractive index = 98%
Density of mixture (CRC) = 0.7976 g/mL
Mass of 9.1 mL sample = 9.1 mL x 0.7976 g/mL = 7.258 g
Mass of methanol in 9.1 mL of sample = 7.258 g x 0.98 = 7.113 g
Volume of methanol in sample = 7.113...