We did a lab on fractional distillation and I am unsure what the three fractions were. I think the first one is ethanol, and the third one is water, but I'm unsure what the middle one is. Would it be an ethanol/water compound? What do you think it would be? Thanks so uch for explaining this.
What were you distilling? Ethanol and water forms an azeotrope of about 95% ethanol/5% water and when the mixture reaches that proportion, the 95/5 stuff is what distills.
To determine the fractions obtained during fractional distillation, you would typically analyze the boiling points of the substances involved. Fractional distillation is a process used to separate a mixture of liquids with different boiling points.
Since you mentioned that the first fraction obtained is ethanol and the last fraction is water, it is likely that you used a mixture of ethanol and water in the lab.
Ethanol has a boiling point of around 78 degrees Celsius, while water has a boiling point of 100 degrees Celsius at normal atmospheric pressure. Therefore, during fractional distillation, the liquid with the lower boiling point (ethanol) would vaporize and rise through the fractionating column, while the higher boiling point liquid (water) would remain as a liquid.
The middle fraction you obtained is likely to be a mixture of ethanol and water, also known as an azeotrope. An azeotrope is a mixture that has a constant boiling point and composition, which means that it cannot be further separated by fractional distillation.
In the case of ethanol and water, an azeotrope with approximately 95% ethanol and 5% water is formed. This mixture boils at a temperature lower than the boiling point of pure ethanol (78 degrees Celsius), so it would be collected as the middle fraction during the distillation process.
Therefore, based on the information provided, the middle fraction is likely an ethanol/water azeotrope with a composition close to 95% ethanol and 5% water.
Note that the exact composition of the middle fraction would depend on various factors such as the initial composition of the mixture, the distillation conditions, and the accuracy of the apparatus used. It is always a good idea to consult the lab procedure or check with your instructor for more precise information regarding the fractions obtained in your specific lab experiment.