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Why Did I Get Strange Results With My Distillation Unknown?

I performed a lab that dealt with finding the melting point of an unknown liquid. The possible liquids are Acetone (56.5 C) Methanol (65.0 C) Ethanol (78.5 C) Isopropanol (82.4 C) Isopropyl acetate (88.8 C) Water (100 C) Toleuene (110.6) Methyl isobutyl ketone (116.9) and 2-Methoxyethanol (124.0 C).

I did the distallation and the highest temp was 70.9 C. So obviously anything above that temp is incorrect. My problem is that I think I possibly performed the simple distillation wrong. While the vapor collected (for every 1 ml collected I wrote down the temperature) the temperature decreased, then increase, then decrease. Then increased but I had to stop the distillation because lab was officially over.

I made a graph of the results (graph attached) and for the life of me I cannot understand how to figure out the boiling point from it. How do I do that? Also why did the temperature fluctuate like that?

Finally I am wondering about writing out chemical equations and mechanisms; When it comes to boiling and melting points is there one to write and if so how? I don't think any mechanisms can be made from melting points and boiling points.

Please explain. Thanks!


Solution Preview

I think you realize that the only time that you can get a reading on a thermometer while doing a distillation is if there is vapor around the bulb of the thermometer. Ideally, you hope to see a quick increase and then a steady plateau at the boiling point of the liquid.

The fluctuations you are describing can sometimes occur when you are not using quite ...

Solution Summary

I outline the reason for seemingly anomolous results with an unknown liquid in a distillation lab.