Ivy Chester, A96024600 A03 CHEM 143A 5/20/13

Lab Report 5: Separation of an unknown two-component mixture by distillation and identification of the components by GC analysis

Introduction:

The purpose of this experiment was to perform a simple distillation as well as a fractional

distillation in order to separate the contents of an unknown mixture (C) by boiling points. This was followed with an analysis by gas chromatography.

In a simple distillation there is the unknown which vaporizes and condenses at which

point it is collected. This is the most basic type of distillation. In this distillation the vapor rises from the boiling solution and condenses once it reaches the condenser where it is immediately collected as a fraction (1). During this process the solution is kept at a constant boil and the temperature is continuously monitored. As the solution boils the component with the lower boiling point will vaporize first and condense into the collected fraction accordingly. It is this difference in boiling points that allows for the different molecules to be isolated (2).

Fractional distillations are set up very similarly to simple distillations, however there is

added a fractioning column. During this experiment the fractioning column was filled with a copper mesh (1). This method is much more effective at isolating the components of a solution due to this fractioning column. The purpose of the column is to increase the surface area. Once the vapors begin to rise into the column they come into contact with the mesh and they condensate and run back down to the solution. This allows for an increased volatility and once the vapors reach the condenser and are collected as fraction they are very pure (3).

Gas Chromatography allows for the analysis of compounds that can be vaporized with

decomposition (4). In gas chromatography there is a mobile phase, in this case helium which acts

as a carrier. There is also a stationary phase within and around a column (4). The compound to be analyzed interacts with the column and both the mobile and stationary phases. This allows that compound to elute at different rates which dictates retention times. It is these retention times that can be compared to each other as well as to standards (1).

Results: Simple Distillation: Temperatures and Volumes

Vile 1 Total Volume (mL) Temperature ℃ 1.0 61 2.0 65 3.0 69 4.0 72 5.0 73 6.0 74 7.0 74 8.0 74 9.0 75 10.0 76 Vile 3 Total Volume (mL) Temperature ℃ 21.0 80 22.0 80 23.0 80 24.0 80 25.0 81 26.0 81 27.0 81 28.0 82 29.0 82 30.0 83

Vile 2 Total Volume (mL) Temperature ℃ 11.0 77 12.0 76 13.0 76 14.0 76 15.0 77 16.0 78 17.0 78 18.0 77 19.0 79 20.0 79 Vile 4 Total Volume (mL) Temperature ℃ 31.0 83 32.0 83 33.0 83 34.0 83 35.0 83 36.0 83 37.0 83 38.0 83 39.0 83 40.0 83

Fractional Distillation: Temperatures and Volumes

Vile 1 Total Volume (mL) Temperature ℃ 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0 67 68 69 69 70 70 70 70 71 71 77 78 79 80 82 83 85 87 89 91

Vile 2 Total Volume (mL) Temperature ℃ 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 31.0 32.0 33.0 34.0 35.0 36.0 37.0 38.0 39.0 40.0 72 72 73 73 74 75 75 75 76 76 92 93 93 93 93 95 92 92 89 76

Vile 3 Total Volume (mL) Temperature ℃

Vile 4 Total Volume (mL) Temperature ℃

Gas Chromatography Analysis:
Distillation Simple Compound 1 n-hexane cyclohexane 2 n-hexane cyclohexane 3 n-hexane cyclohexane 4 n-hexane cyclohexane Area 28948 10791 20753 10608 23323 19763 14827 27484 R.T. 0.886 1.655 0.875 1.645 0.882 1.703 0.879 1.737 Corrected Area 32424.944 10791 23245.643 10608 26124.326 19763 16607.871 27484 % total 75.00% 25.00% 68.70% 31.30% 56.90% 43.10% 37.70% 62.30% Volume (mL) 7.50 2.50 6.87 3.13 5.69 4.31 3.77 6.23 Mol 0.05699 0.02312 0.05220 0.02896 0.04323 0.03985 0.02864 0.05761 0.4972 1.0848 1.8025 Mol Frac. A/B 2.465

Fractional Compound 1 n-hexane cyclohexane 2 n-hexane