Gas Chromatography

In this lab, a hexane and octane mixture was purified, through distillation, to pure octane. The distillation could be completed because part of the solution, hexane, had a lower boiling point than the other, octane, allowing it to evaporate out. Throughout the experiment, four samples were taken and tested by gas chromatography. Gas Chromatography, or GC, was used to analysis the components of each fraction taken during the experiment. Upon looking at the data, the presence of hexane in the fractions decreased, whereas, the presence of octane increased. This was due to the fact that the hexane was evaporating out of the conical reaction vial and collected once condensed in the distillation head. As time progressed, most of the hexane was removed, …show more content…
In the first fraction, hexane was the main substance present. The area under the curve in this chromatogram for hexane was 91.79%, and for octane was 8.21%. This give a ratio of about 92:8 of hexane and octane. This is due to the fact that the boiling point of hexane, 69˚C, is less than the boiling point of octane, 125˚C, and at the temperature at which the fraction was taken, 70˚C to 72˚C, only hexane should have evaporated. This area under the hexane peak slightly decreased in the second fraction. It decreased to 86.25%, while the area for octane increased to 13.75%. This is reasonable, because this fraction was take when the system had the temperature starting at 85˚C and ending at 87˚C. At this temperature hexane is readily evaporating, which is why the fraction mainly consist of hexane, but some octane is evaporating as well, resulting in a slightly higher area at this peak. When analyzing the data, a source of error was found. Fraction 1 and 2 were taken very close to one another, so there was not much change in the …show more content…
This is reasonable, because the temperature at which this fraction was take was between 107˚C and 109˚C. At this point octane has started to evaporate, so the amount in the distillation head has increased. Also with the removal of each fraction, hexane was removed, resulting in mixtures with a higher content of octant. The ratio of this fraction was about 54:46 hexane to octane. If this fraction had a ratio of 50:50, the area under both the hexane peak and the octane peak would be equivalent. The final fraction was taken when the temperature had reached 110˚C to 115˚C. This fraction was taken from the distillation head because the amount left in the conical reaction vial looked to be too small. This resulted in a chromatogram showing the area under hexane peak to be 9.83% and the area under the octane peak to be 90.17%. This is reasonable date because as this experiment progressed, most of hexane should have been removed by the prior fractions or evaporated off. The ratio of 10:90 hexane to octane show that to be the case, however the final fraction should have been 100% octane because ideally all of hexane should have been