Simple Distillation Lab Report

Experiment 3: Simple Distillation of Ethanol-Water Mixture

Purpose The purpose of this experiment was to introduce the technique of simple distillation for the separation of two liquids

Theory Simple distillation uses the difference of two liquids’ boiling points to separate them. The mixture is heated slowly until the boiling point of the first liquid is reached. The lowest boiling point liquid boils off, the vapor is passed through a condensing apparatus, and the condensate is then collected.

Results The first drops of condensation were observed at a temperature of 77.7oC, but the majority of the boiling occurred at 86.3oC. Distillation stopped at 90oC. Accepted ethanol boiling point:78.37oC Initial volume in flask=40 mL Volume of condensate collected=9.9 mL Volume of liquid left in the flask= 27 mL When the cotton swab with the condensate was burned, the swab turned black and was completely burnt When the cotton swab with the remaining fluid in the flask was burned, the swab didn’t burn very well Remaining fluid in the flask had a pungent alcohol smell

Data Analysis A) The boiling point of the condensate= 77.7 °C Accepted ethanol boiling point: 78.37°C Percentage error: 0.86 % As the percentage error is low, the result of this experiment was accurate and some errors that could have resulted from not getting the accepted value can be due vapor loss and heat loss as water vapor was seen on the glass apparatus. B) The percentage of ethanol in the original mixture was 33% and water 67% as nearly 10 mL of condensate was obtained and about 30 ml of liquid was left in the flask obtained from the given 40 mL of solution.

Conclusion

The average boiling point of ethanol was found out to be 77.7°C but the commonly accepted boiling point is 78.37°C. Loss of water vapor during the experiment could have resulted in the low boiling point. But the percentage error was low, so the value obtained is a bit accurate. References PhysicsForums.com Chemguide.co.uk Dictionary.reference.com

Manual Questions 1. The entire bulb of the thermometer must be placed just below the level of the side arm so that it accurately reflects the temperature of the vapor. If it is too high, then the thermometer will read artificially low and if the thermometer is placed too low then it will read higher than the actual temperature of the vapor. 2. Cold water is circulated through the condenser from the bottom so that even if there is a loss in water pressure the condenser will remain full of cold water. 3. An azeotrope is a mixture of two or more liquids in such a way that its components cannot be altered by simple distillation. These mixtures form when the intermolecular forces that attract a molecule to other like molecules are weaker than the forces attracting one molecule to the other type in the mixture. This leads to a mixture that cannot be separated any further by simple distillation. 4. The temperature of the distillation vapor was approximately 77.7oC, which is not much lower than the expected boiling point of pure ethanol (78.4). The reason for this difference is that ethanol and water form an azeotropic mixture. In an azeotropic mixture, the overall boiling point is lower than the boiling point of either of the substituent parts. So the experimental boiling point is within an acceptable range. 5. In theory, the condensate which was collected would be pure ethanol, and the liquid left in the distillation flask should be pure water. In actuality the condensate probably contained a small percent of water, and due to the azeotropic nature of the mixture the distillation flask contained a small percent of ethanol. 6. The total volume of liquid after the distillation was measurably less than the initial volume. Sources that may have contributed to this error are vapor loss, and the condensation that remained on the walls of the apparatus after distillation. These combine sources of error could easily make up the 3.1mL of liquid lost during the process.