Experiment 1- Simple and Fractional Distillation of a Binary Mixture PDF

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Experiment 1: Simple and Fractional Distillation of a Binary Mixture Marneisha Riley Group 6: Gabriella Lang, Bianca Sterr CHM 2210L: Dr.Faeez

Introduction: Distillation is a process often used to separate compounds. Many times, one can use this process to purify and identify any organic compounds that might be present. In other terms distillation is a process by which a liquid is boiled and then it condenses as a vapor above its boiling point3. In order for separation to occur between a mixture of liquids there has to be differences in volatility3. When the vapor has condensed it is more than likely purer than the original mixture. For example, this process can be used to separate a volatile from a nonvolatile product3. Distillation relates to vapor pressure and usually the liquid that has a higher vapor pressure subsequently has a higher concentration and this is often collected first. There are two distillation techniques that are common in the realm of organic chemistry, simple and fractional distillation. Simple distillation consists of boiling the liquid in which you want to separate through a distillation flask. As it is distilling vapor starts to form which goes through a condensing column and then it this vapor then cools and goes back to a state of liquid3. This liquid can then be collected with some type of receiving vessel. This process of distillation works best for compounds that have higher boiling points(20°C-25°C). Factional distillation works best for compounds with lower boiling points(7°C-10°C). This process is similar to that of the simple distillation; however, a fractionating column is added to the distilling flask to allow more separation to occur because the vapor has to go through the fractionating column. Many of the bottled waters and even the gas we put in our cars all go through processes such as fractional distillation4. There are various laws that are used help students, professors and people in the scientific world about more of the process that is going on between the solution in relation to pressure. The first law is Raoult’s Law which states that the partial vapor pressure of the ideal mixture is equal to the vapor pressure of the pure components within the mixture itself1. An ideal mixture is one that obeys Raoult’s

law, for example cyclohexane and toluene are miscible therefore they follow the ideal mixture rules. Another is the Dalton’s law, similar to Raoult’s Law, deals with ideal gases in relation to the total pressure being exerted being equal to the sum of the individual component’s partial pressures1. The concept of azeotropes falls into these laws because it deals with liquids having a specific boiling point and as a result the composition of the mixture cannot be altered1. This shows why some boiling points are lower or higher than the individual components themselves. The aim of experiment 1 is to separate the 1:1 mixture of cyclohexane and toluene by using the processes of simple and fractional distillation.

Experimental Section:

Vial

Add 7.0mL of stock mixture

Vial

Place 2-3 boilig stones in the vial wih the stock mixture

Vial

Set up distillation (Simple or Fractional) Get TA's Approval

#1 For the simple distillation make heat at reasonable rate. For fractional distillation add a fractionating column #4 Collect the estimated amount of 3.5mL for cyclohexane, then raised temperature to 110°C for toluene. Collect estimated amount of toluene left in the distilling flask.

#2 Boil at 81°C for cyclohexane and regulate the heat 34°C/min

#3 Collect distillate and record for every 0.5mL received and the temperature at which it was received.

Table of Chemicals: Name of Chemical IUPAC Name Molecular Formula Molar Mass Boiling Point Melting Point Description Chemical structure

Cyclohexane Cyclohexane C6H12 84.16 g/mol 81°C 6.47°C Flammable and colorless Cyclohexane

Toluene Methylbenzene C6H5CH3 92.14 g/mol 111°C -95°C Flammable and colorless

Toluene CH3

Results: Table #1: Data Collected from Simple and Fractional Distillations VOLUME (mL) Simple Distillation (°C) 0.5 62 1.0 68 1.5 72 2.0 79 2.5 81 3.0 83 3.5 87 4.0 93 4.5 99 5.0 105 5.5 105 6.0 101 6.5 95

Fractional Distillation(°C) 54 61 68 70 65(Toluene Switch) 62 62 68 72 75 ----------------------

Distillation curves for Simple and Fractional distillation 120

Teamperature (°C)

100 80

Sample Calculations:

60

Percent Recovery for Cyclohexane (Simple Distillation): Percent Recovery = (Actual Yield/Theoretical Yield) x 100% % Recovery = (3.4mL/3.5mL) x 100% % Recovery = 97.14%

40 20 0 0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

Volume of Distillate (mL) Simple

Fractional

Figure 1: Distillation Curves

Percent Recovery for Toluene (Simple Distillation): Percent Recovery = (Actual Yield/Theoretical Yield) x 100% % Recovery = (3.1mL/3.5mL) x 100% % Recovery = 88.57%

6

6.5

Percent Recovery for Cyclohexane (Fractional Distillation): Percent Recovery = (Actual Yield/Theoretical Yield) x 100% % Recovery = (2.5mL/3.5mL) x 100% % Recovery = 71.43% Percent Recovery for Toluene (Fractional Distillation): Percent Recovery = (Actual Yield/Theoretical Yield) x 100% % Recovery = (3.0mL/3.5mL) x 100% % Recovery = 85%

Discussion: The percent recovery for both cyclohexane and Toluene were of good percentage for simple distillation, both were well over 80% which shows that a good amount of both cyclohexane and toluene were recovery after the chemical reaction was completed. There was 3.4mL of Cyclohexane collected, as well as 3.1mL of Toluene during this process. In the simple distillation about 6.6mL of the chemical reaction was collected overall, which means over 90% of the stock solution went through a chemical reaction. During fractional distillation the percent recovery is much lower, Cyclohexane had a low percentage at 71.43% while Toluene had 85% recovery. Both percentages were still above 70% however they were still low in comparison to those in the simple distillation. About 5.5mL of the chemical reaction was collected overall during the fractional distillation, meaning 78% of the stock solution with through a chemical reaction. These low percent recoveries were due to sources of error. During the fractional distillation set up, the connector from the condenser to the distillation head and fractionating column leaked out much of the product in the beginning of this experiment. This leakage caused product to get lost which then affected percent recovery because that product was not accounted for. It is seen in figure 1 that the curves both decrease at around the 2mL-3.5mL range which indicates the switch from cyclohexane to toluene in the distillation process. Moreover, it is seen that simple distillation worked

better for the miscible mixture of cyclohexane and toluene, which is due to the fact that they have a higher boiling difference and simple distillation is more efficient in relation to those compounds who have higher boiling differences.

Conclusion: The main aim/objective of this experiment was to see how techniques of distillation work by using cyclohexane and toluene to separate from one another. This process was done by both simple and fractional distillation. Based on the data accounted for and the graph that was created one can see that simple distillation was the better distillation technique method for this compound. This corresponds to simple distillation being able to account for compounds that have higher boiling differences such as cyclohexane and toluene. In the real world we see these processes done every day like our drinking water. Distillation can remove many of the contaminants and impurities within the water itself using a distiller2. Some of these contaminants include calcium and magnesium which are two of the main causes for water hardness2.

This experiment overall accomplished what it was set out to do. The distillation techniques were learned, and the data collected showed which method favored compounds with higher or lower boiling differences. Many of these techniques can be applied to many of our real-world things such as oil and water.

References

1) Libretexts. (2019, June 5). Raoult's Law and Ideal Mixtures of Liquids. Retrieved from https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supple mental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Physical_Equilibria/Raoult's_Law_ and_Ideal_Mixtures_of_Liquids 2) Skipton, S. O. (2008, December). Drinking water treatment. Retrieved from http://extensionpublications.unl.edu/assets/pdf/g1493.pdf 3) weldegirma, solomon. (n.d.). Experimental Organic Chemistry Lab Manual (7th ed.). Pro-Copy , Inc. . 4) (n.d.). What is Fractional Distillation? Retrieved from https://study.com/academy/lesson/what-isfractional-distillation-definition-process.html...