April Rose C. Mirasol
Co-workers: Mumtaz O. Kunhammed
Kirstie Charis E. Curato
Chem 74.2
Date Performed: April 20, 2009
Date Finished: April 21, 2009
DISTILLATION OF BINARY LIQUIDS
OBJECTIVE:
The determination of the necessary data for the construction of a boiling-point-composition
diagram for the acetic acid-water system.
EQUIPMENT:
Burette
Pipette
Erlenmeyer Flasks
Distilling Flask
Graduated Cylinders
Water Condenser
Spatula
Thermometer
Submersible Pump
Iron Clamp
Boiling Chips
Volumetric Flask
Dessicator
Burette Clamp
Hot Plate
Adapter
Iron Stand
Aspirator
Weighing Bottle
Beaker
CHEMICALS:
Glacial Acetic Acid
NaOH
KHP
Phenolphthalein
Distilled Water
DISCUSSIONS:
Distillation of binary liquid systems that form miscible mixture is based on the act that at any
given temperature, the vapor above any solution is richer in the more volatile substance than the solution.
When the vapors are condensed and the new vapor above the condensate removed, the new vapors will be
found considerably richer in the more volatile constituent than in the solution from which they come. By
repeating this process, it is possible to obtain a concentration of the more volatile constituent in the vapor
and a concentration of the less volatile constituent in the solution. The boiling point of two liquids is the
sum of the partial vapor pressure of the two liquids which is equal to the atmospheric pressure.
If the attractive forces between unlike molecules are greater than between like molecules, then the
total pressure will be less than that predicted by Raoult’s Law; if the attractive forces between unlike
molecules are less than between like molecules, then the total pressure will be greater than that predicted
by Raoult’s Law.
Distillation method is usually conducted at constant pressure than at constant temperature. At a
given confining pressure, any solution of definite composition will boil at a temperature at which the total
vapor pressure of the system becomes equal to the confining pressure.
A boiling-point-composition-diagram consists of two curves on the same graph: (1) a plot of the
composition of a liquid against its boiling point (2) a plot of the composition of the vapor equilibrium
with the liquid and its boiling point.
PROCEDURE:
100 mL of glacial acetic acid was mixed with 2 mL of water and was then poured, along with
some boiling chips, into a 250 mL distilling flask equipped with a thermometer, condenser and adapter.
Then 1 mL sample of this solution was taken using a pipette and placed into an Erlenmeyer flask labeled
L-1. The mixture was slowly distilled, until 10 mL of the distillate had been collected in a clean, dry 10
mL graduated cylinder; the burner was then removed. The temperature was recorded when 5 mL of the
distillate had been collected. Another 1 mL sample of the solution remaining in the distilling flask was
taken and added to the flask L-1. At the same time, 2 mL of the distillate was taken and placed into
another Erlenmeyer flask labeled V-1. These samples were then titrated with the standardized NaOH,
using phenolphthalein as the indicator.
For Run No. 2, 5 mL of water was added o the residue in the distilling flask and was distilled over
several millimeters in order to wash out the condenser. After washing out the condenser, the heating was
stopped and 1 mL sample from the distilling flask was taken into an Erlenmeyer flask L-2; 10 mL was
distilled, recording the temperature when 5 mL has been distilled. The heating was again stopped and 1
mL of the residual liquid was taken from the distilling flask into flask L-2 and 2 mL of the distillate from
the graduated cylinder into V-2. Three additional runs (3, 4, and 5) were carried out, adding 10, 20 and 30
mL of water, respectively.
DATA AND RESULT:
Table I - Standardization of 1 N NaOH:
Trial I
0.5267
3.00
0.8598
Weight of KHP, g
Volume of NaOH used, mL
Normality of NaOH
Average Normality of NaOH
Trial II
0.5160
3.00
0.8423
0.8511
Table I - Summary of Results:
Run No.
Temperature, oC
1
2
3
4
5
109
107
104
101
100
Volume of NaOH, mL
L
V
39.10
38.60
37.80
36.60
35.70
30.80
28.50
22.20
20.10
15.30
Conc. of CH3COOH, N
L
V
16.6390
16.4262
16.0858
15.5751
15.1921
13.1069
12.1282
9.4472
8.5536
6.5109
Table I - Conversion from Normality to Mole Percent:
Concentration of CH3COOH, mole %
L
V
83.19
80.11
75.52
69.26
64.95
46.39
39.74
27.67
22.01
14.92
Run No.
1
2
3
4
5
CALCULATIONS:
To prepare 500mL of 1 N NaOH, the amount of NaOH pellets needed:
1 N NaOH = 1 M NaOH
Weight of NaOH = 0.50 L x 1 mol NaOH/ 1 L x 40.0 g NaOH/ 1 mol NaOH
= 20.0 g
Calculation for Concentration of NaOH (N):
Normality of NaOH =
Wt. of KHP
204.2 g/mol
x 1 mol NaOH
1 mol KHP
Vol. of Solution
For Trial I:
Normality of NaOH =
0.5267 g KHP x 1 mol NaOH
204.2 g/mol
1 mol KHP
0.002 L
Same calculation was done to trial II:
Calculation for Concentration of CH3COOH (N):
Normality of CH3COOH =
Volume of NaOH x Conc. of NaOH x 1 mol CH3COOH
1 mol NaOH
Volume of CH3COOH
For L-1:
Normality of CH3COOH =
0.03910 L NaOH x 0.08511 N NaOH x 1 mol CH3COOH
1 mol NaOH
0.002 L CH3COOH
= 16.6390 N
For V-1:
Normality of CH3COOH =
0.03860 L NaOH x 0.8511 N NaOH x 1 mol CH3COOH
1 mol NaOH
0.002 L CH3COOH
= 16.4262 N
Same calculations were done for L-2 to L-5 and V-2 to V-5 and they were summarized above.
Calculation for the Conversion to Mole % of CH3COOH:
Mass of solution = 1.06 g/mL solution x 2 mL solution
= 2.12 g solution
For L-1:
Mole of CH3COOH = 2 mL x 16.6390 mol/ L NaOH x 1L/ 1000mL = 0.03328 mol
Mass of CH3COOH = 0.3328 mol x 60.06 g/mol CH3COOH = 1.9988 g
Mole of H2O = 2.12 g solution – 1.9988 g CH3COOH
18.02 g/mol
Mole % of CH3COOH =
= 6.7258 x 10 -3 mol
0.03328
x 100 = 83.19 %
0.03328 + 6.7258 x 10 -3
For V-1:
Mole of CH3COOH = 2 mL x 16.4262 mol/ L NaOH x 1L/ 1000mL = 0.03285 mol
Mass of CH3COOH = 0.3285 mol x 60.06 g/mol CH3COOH = 1.9730 g
Mole of H2O = 2.12 g solution – 1.9730 g CH3COOH = 8.1576 x 10 -3 mol
18.02 g/mol
Mole % of CH3COOH =
0.03285
x 100 = 80.11 %
0.03285 + 6.7258 x 10 -3
Same calculations were done for L-2 to L-5 and V-2 to V-5 and they were summarized above.
CONCLUSION:
From this experiment, the necessary data to construct a boiling-point composition diagram for the
acetic acid-water system was determined. It is noticeable that the plots were not smooth which shows that
errors had been incurred. These errors may result on the inefficiency of the method, on the instruments
used in the set-up, and may be due to personal errors by the experimenters incurred probably mostly
during titrations.
REFERENCE:
Fundamentals of Physical Chemistry by Maron and Lando