Fractional Distillation Essay

Discussion

The main objective of this experiment is to identify the two solvents that makeup the unknown solution. In addition to identifying, determining the ratio of that said mixture is the secondary aim of this experiment. In order to identify the unknown mixture of the two solvents, fractional distillation must be used to gather that information. Gas chromatography is used as a method of separation as well but, gas chromatography can determine the ratio of the mixture whereas fractional distillation cannot. Though there are a multitude of ways to separate mixtures, in this lab due to the unknown solution being a liquid/liquid mixture fractional distillation serves as the best method of separation. With distillation, the main criteria
Fractional distillation is used on mixtures whose boiling point difference is less than or equal to 40C - 50C. It is possible to use simple distillation to distill but the result will be unpurified components. While simple and fractional distillations apparatuses look similar, fractional distillation uses an additional column located in between the distillation flask and distillation head. This fractional distillation column creates a large temperature gradient because the lower part of the column is hot while the upper half is not as hot. With this, the vapor rising distances itself from the heat source; in turn, the vapor will reach a point to where there is not enough energy to keep all of the vapor molecule as a gas, causing it to condense. Gravity takes over and most of the vapor falls back into the flask and the boiling point decreases as a result. There is then enough energy to revaporize a small percentage which begins to move up the column again. It is later condensed and the process of revaporizing and condensing is carried out all the way to the top until it is at 100% vapor. This is similar to a series of simple distillations but just in one big step. In order to successfully do a fraction distillation, certain requirements must be met, 1) There must be close contact between the liquid and vapor phases. Using secure apparatus with connected joints can achieve this. 2) Maintenance of the proper temperature gradient. As stated before, moving up along the column, the boiling point should decrease as the vapor particles move farther away from the heat source. 3) Using the correct length of the fractional distillation column. Using the incorrect length can result in improper isolation of the solvents. 4) The difference in boiling points of the mixture should be no less than 20C - 30C. Once these conditions have been met, fractional distillation can be done. At any given