Fractional Distillations Essay

In this experiment we aim to show that we can divide two volatile compounds from a mixture due to the different chemical belongingss of each compound. We will carry through this by a separation process known as distillment. which relies on each compound holding a distinguishable and separate boiling point. Our pure merchandises will be analyzed with gas chromatography to find the success of the distillment. Procedures

The experiment was performed as stated in the class text edition: Pavia. D. L. . Lampman. G. M. . Kriz. G. S. . Engel. R. G. Introduction to Organic Laboratory Techniques: A Microscale Approach. 2007. 4th Ed. Pp 51—57. . Datas

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The distillment curves for our simple and fractional distillment ( See page 3 ) clearly demonstrate that fractional distillment separates the two compounds more wholly. The boiling point ( bp ) of our unknown compounds was taken from the level parts of the fractional distillment curve. Our unknown mixture contained hexane ( bp 69 ?C ) and methylbenzene ( bp 110. 6 ?C ) . Analysis via gas chromatography allowed us to find the comparative per centum of hexane and methylbenzene at fractions near the beginning and terminal of our distillments. Relative per centums have been recorded in the tabular array below. and our computations are shown on page 5.

This hebdomad we utilized two methods of distillment ( simple and fractional ) to divide a mixture of two volatile compounds. We found that while the simple distillment separated the bulk of the two compounds near the beginning and the terminal of the distilling procedure. fractional distillment produced much more pure fractions. In simple distillment the column was shorter. leting less room for the two different compounds to to the full divide. While heating the round-bottom flask the hexane molecules gain higher kinetic energy faster than the methylbenzene molecules due to their lower molecular weight and lesser intermolecular forces. The longer fractional distillment column allowed the hexane molecules with higher kinetic energy to divide from the lower-energy methylbenzene molecules.

After sing the gas chromatograph informations from the fractional distillment we saw that our unknown compounds had about wholly separated. while the fractions from the simple distillment were less pure. Although distillment is a good separation technique it is still necessary to guarantee that proper stairss are taken to cut down the opportunities of mistake. Failure to add a boiling bit to the round-bottom flask could let the mixture to heat unevenly. This could let molecules with a higher boiling point to derive kinetic energy before the molecules with the lower boiling point. which would make impure fractions. Watching the rate of temperature addition is besides of import. Leting the temperature to increase excessively rapidly can do dross for the same ground.

We forgot to add the boiling bit to the round-bottom flask in the simple distillment. which could hold contributed to the mixture of methylbenzene and hexane that we saw. We made certain to include the boiling bit in the fractional distillment. nevertheless. and did non detect any jobs. Even though both hexane and methylbenzene are volatile. they have different chemical belongingss to let for separation and analysis. Hexane is a hydrocarbon with no dipole minute or dual bonds. This means that it has few intermolecular interactions. and will hold a lower boiling point. It besides has a lower molecular weight than methylbenzene. so it will look foremost on the gas chromatograph.

Toluene has a benzine pealing with a methyl group attached. Toluene has greater intermolecular forces than hexane because the benzine pealing withdraws negatrons from the methyl group. This creates a little mutual opposition to the molecule that increases intermolecular forces and increases the boiling point. Since methylbenzene has a greater molecular weight than hexane it will look 2nd on the gas chromatograph. This experiment illustrates how utile the different belongingss of compounds can be while seeking to sublimate mixtures of compounds.


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