Distillation Of Cyclohexane And Toluene Lab Report

Title: Distillation of Cyclohexane and Toluene

Introduction: The experiment was conducted to show which type of distillation is the most accurate in separating the two liquids. Simple distillation results were compared to the different techniques of fractional distillation in order to show which was the most accurate in separating the liquids.

Procedure: This experiment followed the directions present in the manual for the simple distillation method. 15 mL of the Cyclohexane and Toluene solution was used in the distillation flask and the heating mantle was initially set at 25V. Eventually, our TA suggested to turn up the heating mantle to 50V because the liquid was not boiling after 20 minutes of heat. After the forerun was disposed,

the collection of the first fraction began at 79oC. During the experiment, the temperature never leveled or dipped after the collection of the first fraction; therefore, with the advice of our TA, the collection of the second fraction started once the temperature reached 95oC and ended once the temperature leveled off at 100oC.

Results:
Temperature
Total Volume Collected
26oC
0 mL
88oC
1.5 mL
90oC
2 mL
91oC
3 mL
92oC
3.5 mL
94oC
4 mL
95oC
5.3 mL
96oC (beginning of second collection)
7.3 mL (2 mL from second collection)
98oC
8.1 mL (2.8 mL from second collection)
100oC
8.3 mL (3 mL from second collection)
100oC
9.1 mL (3.8 mL from second collection)
The table above shows how the total volume collected steadily increased as the temperature of the solution increased.

Volume of collections and Index of Refractions:
Fraction
Volume
Index of Refraction
Undistilled Liquid
15 mL
1.470
First
5.3 mL
1.450
Second
4.1 mL
1.467
Residual
3.6 mL
1.494
The table above shows how the composition of the different fractions are related to each other. The first fraction contained a higher mole fraction of cyclohexane than the original solution, while the residual fraction contained a higher mole fraction of toluene than the original solution.

Conclusion: Of the original 15 mL solution, only 13 mL was recovered at the end from the two fractions and the residual liquid. The missing liquid could have leaked out if the joints were not properly clamped together, or some of the material could have stuck to the glass equipment and was therefore not counted in any of the fractional measurements.

The composition of the different fractions are related to the different temperatures at which the fractions were collected.

For the first fraction, it was collected at temperatures between 79oC and 95oC. Based on the boiling point of Cyclohexane being 80.7oC and the boiling point of Toluene being 111oC, the first fraction should have been almost completely composed of Cyclohexane. The second fraction was collected at temperatures between 95oC and 100oC and should have been mostly composed of Toluene because the majority of the Cyclohexane should have been in the first fraction. Since the residual liquid was the liquid that had not boiled at a temperature of 100oC, then almost all of that remaining liquid should have been

Toluene.

In comparing the average mole fraction of Toluene for each fraction of each set-up, the fractional distillation with any type of packing has a significantly smaller mole fraction in the first fraction, which is supposed to be almost pure Cyclohexane.

The average mole fraction for the different types of fractional distillation with packing is less than 0.15; the fractional distillation packed with steel wool had the lowest mole fraction at 0.1386139 and the simple distillation set up had the highest mole fraction at 0.336633663. In the second fraction the mole fractions varied significantly between the different setups. The fractional distillation with steel wool had the lowest average at 0.5293501, while the fractional distillation with the empty column had the highest average at 0.821075. The fractional distillation with beads (mole fraction of 0.7008487) and rings (mole fraction of 0.7095746) had very similar average results, while the simple distillation had a mole fraction of 0.557708628. In the residual fraction, which was supposed to be almost pure Toluene, all of the distillation setups had mole fractions of Toluene above 0.94. The fractional distillation with the empty column had the highest average mole fraction with 0.97843 and the fractional distillation with the steel wool had the lowest average mole fraction with 0.9466054. While the fractional distillation with the empty column had the purest residual liquid remaining, the individual data points for all the

fractions varied significantly more than the individual data points for the fractional distillation with steel wool, beads, or rings. This shows that using packing produces more accurate results in terms of the mole fraction compared to the fractional distillation with an empty column or simple distillation setups.

Multiple solutions could be used to improve the results of the distillation. If the temperature of the heating mantle is decreased but still high enough to boil the first liquid, that will help ensure less of the higher boiling point liquid will be collected in the first fraction. For fractional distillation, any way that you can increase the surface area that the vapor goes through in the column will help improve the distillation process. This can be done by increase the length of the column so the vapor goes through a longer length of packing material.

Based on the data collected, it shows that fractional distillation is significantly more accurate than simple distillation or fractional distillation with an empty column. While the samples collected in the fractional distillation were not completely pure, they were much closer than the simple distillation. The reason there were still imperfections in the fractional distillation processes could have been not enough packing was used in order to save time. The samples collected could have been closer to their pure form; however, the distillation process would have taken much longer due to the extra packing in the column.