Lab Report 2 3n4d5d

CHM 1321D- Organic Chemistry

LAB REPORT EXPERIMENT N0 2

Purifying Chemicals by Distillation Thursday, 02nd February 2017 Name: Magloire Segla Student #: 8363344 Lab Partner: Sara Nasr (8173184) TA: Philip Eckert ([email protected])

CHM 1321D- Organic Chemistry Procedure: Please refer to the lab manual Observations: 



Part 1: Simple distillation  Our mixture of 25mL containing 2-propanol and 1-butanol was a clear and colorless solution.  Heat was set at 80⁰C in order to get the solution boiling, and then lowered at 75⁰C after getting 5mL of solution in the receiving flask.  A few minutes in the experiment, distillate drops could be seen in the receiving cylinder.  Temperature jumped initially from 48 to 84⁰C, and stayed relatively constant despite its steady rise. Part 2 : Fractional distillation  In the first few minutes of this part, vapor was not reaching the top as the fractioning column stayed cool. Aluminum foil was used to insulate both our distilling flask and our distillation head.  We observed a drastic increase in temperature after insulation: 24.1⁰C to 82.9⁰C.  The thermometer bulb was placed at the outlet from the fractioning column

Results: Figure 1: Table for Temperature/ml of distillate in Simple Distillation Volume of Distillate (mL) 1mL 2 mL 3 mL 4 mL 5 mL 6 mL 7 mL 8 mL 9 mL 10 mL 11 mL 12 mL 13 mL 14 mL 15 mL 16 mL

Temperature of Distillate (oC) 26.1oC 84.4 oC 84.6 oC 84.9 oC 86.3 oC 86.7 oC 86.9 oC 87.1 oC 87.6 oC 88.3 oC 88.7 oC 88.9 oC 89.1 oC 96.0 oC 108.5 oC 108.7 oC

CHM 1321D- Organic Chemistry 108.8 oC 112.8 oC 114.5 oC 115.2 oC 117.0 oC 117.3 oC 117.4 oC 117.7 oC 117.7 oC

17 mL 18 mL 19 mL 20 mL 21 mL 22 mL 23 mL 24 mL 25 mL

Figure 2: Graph of Relationship between Temperature and Volume of Distillate for Simple Distillation 110 100

Temperatu re of Distillate (⁰C)

90 80 70 60 50 40 30 20 10 0 0

2

4

6

8

10

12

14

Volume of Distillate (mL)

16

18

20

22

24

CHM 1321D- Organic Chemistry

Figure 3: Table for Temperature/ml of distillate in Fractional Distillation Volume of Distillate (mL) 1mL 2 mL 3 mL 4 mL 5 mL 6 mL 7 mL 8 mL 9 mL 10 mL 11 mL 12 mL 13 mL 14 mL 15 mL 16 mL 17 mL 18 mL 19 mL 20 mL 21 mL 22 mL 23 mL 24 mL 25 mL

Temperature of Distillate (oC) 24.1oC 82.9 oC 83.0 oC 83.3 oC 84.1 oC 84.4 oC 84.9 oC 86.2 oC 86.5 oC 87.4 oC 87.6 oC 90.0 oC 93.7 oC 94.4 oC 101.6 oC 106.8 oC 109.8 oC 113.8 oC 115.3 oC 116.5 oC 116.9 oC 116.9 oC 117.0 oC 117.2 oC 117.5 oC

CHM 1321D- Organic Chemistry

Figure 4: Graph of Relationship between Temperature and Volume of Distillate for Fractional Distillation

110

Temperatu re of Distillate (⁰C)

100 90 80 70 60 50 40 30

20 10

0 0

2

4

6

8

10

12

14

Volume of Distillate (mL)

16

18

20

22

24

CHM 1321D- Organic Chemistry

Figure 4’: this is what the Graph of the Relationship between Temperature and Volume of Distillate for

Fractional Distillation should look like (taken from Sara Nasr).

Temperatu re of Distillate (⁰C)

Volume of Distillate (mL)

CHM 1321D- Organic Chemistry

Discussion: Distillation is a method that consists in separating two or more compounds on the basis of their boiling points: liquids are vaporized and the vapors are condensed and collected. Part 1: The simple distillation although faster, is not as effective as the fractional distillation. We can see by looking at the various graphs in the lab manual and at figure 1 above that there is no evident separation of the compounds in the mixture: absence of an immediate spike, but instead we have a steady slope increase. The rise that we observe from both the experimental data (figure 1) and the graph above (figure 2) occurs at approximately 14-15mL. Looking at the 2 compounds in our mixture and for us to determine the boiling points of each, we must look at their molecular size as both compounds contain the functional group characteristic of alcohols: OH. 2-propanol evaporates first: its fewer number of atoms results in much more smaller molecules , and thereby the overall compound displays less intermolecular forces (induced dipoles from Van der Waals forces) when compared to the 1-butanol. It will therefore take less energy to change the 2-propanol’s state from liquid to gas: we observe on figure 2 the evaporation of 2-propanol at a temperature of approximately 90⁰C. 1-butanol evaporates second and last: its higher number of atoms results in much bigger molecules, and thereby shows a compound that has a greater amount of intermolecular forces: it has the highest boiling point of the two compounds – approximately 120⁰C. Part 2: Fractional distillation is a process that can be described as the separation of a mixture into its components parts, and doing so by separating chemical compounds by their boiling point. By adding a fractioning column in Fractional Distillation, we have the ability to create a pure mixture. The texture of the column and its packing material will make place for a series of condensations and evaporations to happen in order to enrich the vapor in the lower boiling component. Each condensation-vaporization cycle enriches the vapor in 2-propanol and returns some condensate, enriched in 1-butanol, to the distilling flask. Enough cycles will result in an effective separation of the vapors. As viewed earlier, the 2-propanol with the lowest boiling point (approximately 90⁰C) will evaporate first and the 1-butanol with the highest boiling point of the two compounds (approximately 120⁰C) will evaporate last. The peak in temperature that begins at approximately 14mL shows the evident separation between the two compounds boiling points.

Source of Errors:

CHM 1321D- Organic Chemistry A number of various sources of errors could lead to slightly skewed results during this lab. The first source of error could have been the distilled substance: the simple distillation resulted in a distillate of approximately 1mL more than the wanted 25mL. Another important source of error that must be discussed is the error (human error) of measurements: reading graduated equipment or in this particular case graduated cylinders is always a process prone to error. Being required to stay out of the fume hoods, we are forced to read the measurements at a distance. Another source of error could be what I mentioned earlier in Observations: the heat was 80⁰C at first in order to bring the solution to a boil, and then quickly switched to 75⁰C when we had 5mL of distillate in the receiving flask. A possible source of errors for both distillation processes could also include inadequately sealed ts in glassware and residual distillate left in the distillation apparatuses: not tightly sealed ts could have led to vapor loss leading to a smaller volume of collected distillate.

Questions: 1. It is really important to have liquid flowing back through the fractional column in order to get a good separation of the compounds. The column in a fractional distillation is responsible for the increase of the surface area (it “provides a surface for the vapor to condense on as the distillation proceeds)to obtain an even better number of condensations and vaporizations of the solutions: the compound with the lower boiling point will evaporate up the column, while the compound that has the higher boiling point condenses and flows back into the flask in what we could call a cyclic fashion; this will then lead to a more effective separation of the compounds. 2. A fractionating column can be insulated to provide a smooth temperature gradient. Maintaining a uniform temperature gradient within a fractionating column is important because the whole process of distillation heavily relies on the concept of temperature: it is necessary for proper separation of the components. As the vapor moves up the column, temperature will decrease away from the heat source; this will result in the compound with the higher boiling point converting back to liquid and condensing at the lower area. The temperature gradient uses various condensation-vaporization cycles throughout the process to separate the different compounds: in the end we then have a maximized amount of the lower boiling point component in the receiving flask.

CHM 1321D- Organic Chemistry 3. The vapor pressure of benzene at 81⁰C is equal to the atmospheric pressure or 101.325kPa: this is because the boiling point of a compound is defined when its vapor pressure equals the atmospheric pressure. 4. If we were to increase the atmospheric pressure, the compounds’ vapor pressure has to increase to reach an equivalence point: the boiling point will increase as a result. Applying more pressure to the molecules will make them more rigid; it will then require more energy to break the bonds and turn the appropriate compound into a gaseous state. (Gay-Lussa’s law: as pressure increases, so does temperature). 5. Cooling water must enter the bottom of the condenser and not the top because we need to assure an efficient cooling: water being filled at the bottom is being filled against gravity (it is fighting against it). We need to note that it is important that the condenser fills up with water as this will maximize the condensation of the vapor back into liquid form: the result is an increased speed and accuracy of the distillation.

6. According to Raoult’s Law, P Total = PA × NA + PB × NB; where P represents the partial pressure of each compound, and N is the mole fraction of each compound in the mixture. As a result: P mixture = (350mmHg)(0.75) + (150mmHg)(0.25) = 300 mmHg The vapor pressure of a 3:1 mixture of A and B at 95⁰C is 300 mmHg.