Molecular Weight of Volatile Liquid Using Dumas Method

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OBJECTIVE:
* To determine the molecular weight of a volatile liquid by using Dumas method. METHOD:
MATERIAL| CHEMICALS|
125 mL Erlenmeyer flask| Known liquid (2-propanol)|
Rubber band| Unknown liquid|
Boiling chips| |
Watch glass| |
100 mL graduated cylinder| |
Pin| |
600 mL beaker| |
Hot plate| |
Thermometer| |
Room temperature water| |
6 × 6 and 8 × 8 aluminium foil| |
PROCEDURE:

SAFETY
* Lab Coat and Safety Goggles.
* Keep the bottles tightly close when not in use.
* Do not drink or eat in laboratory.
OBSERVATION:
Weight balance detail:
Instrument Number| 5|
Model Number| MS204-S/03|
Manufacturer| METTLE TOLEDO|
Type| New Classic MF|
Boiling chips detail:- VWR scientific, Inc.
Porous boiling chips
VWR cat. # 26397 - 409
Given sample: - 2-propanol (CH3CHOHCH3)
Molecular weight: - 60.08 gm/mole
Sample volume taken: - 2 mL
| Flask 1| Flask 2| Flask 3|
Mass of flask and condensed vapour| 77.8735 gm| 77.8768 gm| 77.8750 gm| Mass of empty flask apparatus| 77.6050 gm| 77.6059 gm| 77.6055 gm| Mass of condensed vapour| 0.2685 gm| 0.2709 gm| 0.2695 gm|

| Flask 1| Flask 2| Flask 3|
Temperature of water| 90˚C (363 K)| 93˚C (366 K)| 95˚C (368 K)| Barometric pressure (Assume)| 1 atm| 1 atm| 1 atm|

| Flask 1| Flask 2| Flask 3|
Volume of flask| 147 mL| 143 mL| 143 mL|
Temperature: - 93˚C (366 K)
Pressure: - 1 atm => 760 mmHg
PV=nRT n = W/M where, R = 0.0821 atm.L/mol.K Flask 1: - M = WRT= 0.2685 × 0.0821 × 363
PV 1 × 0.143
* 55.9574 gm/mole
Flask 2: - M = WRT= 0.2709 × 0.0821 × 366
PV 1 × 0.143
* 56.3889 gm/mole
Flask 3: - M = WRT= 0.2695 × 0.0821 × 368
PV 1 × 0.143
* 56.9395 gm/mole
Average = 55.9574 + 56.3889 + 56.9395
3
* 56.4286 gm/mole
% error = Accepted value – experiment value × 100...
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