In this lab, we will be purifying two liquids in a mixture using distillation then verifying their purity. Due to their different boiling points, distillation is used to vaporize, condense, and separate the liquids. Using the rferactive index, we will create a callibration curve to further identify purity. Purity will also be assed using both simple and fractional distillation methods.

Through this lab, I will learn different distillation techniques, properties of each compound, and how to effectively utilize them to purify a substance.

1. Refraction is the bending of a light ray from one medium to another and seeing how the angle changes. In this lab, we're using the refractive index to test for purification as each compound has a unique refractive index.

2. The best compounds to be separated by distillation are those that are liquid at room temperature.

3. Fractional distillation is the separation of liquids within a homogenous mixture. It involves multiple rounds of condensation and vaporization to truly separate the liquids which is done efficiently within a fractionating column. Their differences in vapor pressure separate these compounds using this technique.

4. It's important not to overheat the flask during distillation because the compound with the higher boiling point will distill quickly within the early fractions which will mess with the refractive index.

5. It's important to put grease in the glass joints to ensure perfect sealant. Glass joints aren't perfectly airtight so grease fixes that issue. If too little is used, it could result in a bad seal while too much could lead to contamination dissolving the solvent.

6.  Cold water running through the condenser allows for a higher yield of the substance you're trying to isolate.

7. An azeotropic mixture is a mixture that is composed of the same amount of liquid and vapor phases. Azeotropic distillation is when another component is added to better separate the components. Water or benzene is usually added to separate the components within the azeotropic mixture.

8. Steam distillation is utilized when the boiling point of the liquid substance being distilled is higher than water.

9. Vacuum distillation is used when the boiling point of the compound is extremely high. It's used to distill the compound without significant decomposition.

10. The purpose of activity #1 is to create a calibration curve of various solutions that examine the purity of a substance without having to test for purity.

11. The cyclohexane will be distilled first because it has the lower boiling point and therefore, will be vaporized first.

12. The difference between the two distillations is the simple and fractional distillations. Simple distillation is used when compounds have similar boiling points while fractional is used when boiling points are not as close. Simple distillation should be more effective as it's curated towards boiling points past a 25-degree Celsius boiling point range from each other which the two compounds are as the difference between their boiling points is 32 degrees Celsius according to literature values.

-Tested the Refractive Index for 50% cyclohexane with 50% toluene and 25% cyclohexane with 75% toluene

-The solutions were made according to the proper ratios and two drops were placed in a tool that measured the refractive index

-Our calculated values were 1.4617 for 50 % cyclohexane with 50% toluene and 1.4763 for 25% cyclohexane with 75% toluene

-The class average was  1.4634 for 50 % cyclohexane with 50% toluene and 1.4753 for 25% cyclohexane with 75% toluene

-The table of values and chart are shown below

% Cyclohexane Avg. RI Values

100% 1.4241

75% 1.4409

50% 1.4634

25% 1.4753

0% 1.4946

Looking at the graph and the data, as the % of cyclohexane in solution was increased, the refractive index was lowered. The refractive index of the solution and the % cyclohexane composition are inversely related. On the contrary, as the % toluene in solution increased, so did the refractive index. Toluene in the solution and the refractive index are directly related.

The line itself was mostly linear as shown within the R^2 value being almost 1. This shows the correlations described above.

-The simple and fractional distillation was setup according to the picture provided in the text book. The water source was connected from the fractional to the simple, than into the drain creating a cool chamber for condensation.

Simple:

-60 mL of solution, composed of 30 mL cyclohexane and 30 mL toluene for a 1:1 ratio, was placed into the round bottom flask. 

-The flask was then heated to a boil allowing steam to travel up through the chamber and then condensed.

-Every 3 mL of distillate was set aside and tested for the refractive index.

-When the 3 mL were set aside, the temperature was also taken.

-This process was continued until the refractive index was close to the refractive index in class for 0% cyclohexane and 100% toluene which was about 45 mL for our lab group.

Fractional:

-60 mL of solution, composed of 30 mL cyclohexane and 30 mL toluene for a 1:1 ratio, was placed into the round bottom flask. 

-The flask was then heated to a boil allowing steam to travel up through the chamber and then condensed.

-The first drop of distillate was about an hour and 15 minutes after the fractional distillation process had started.

-The same process was repeated for every 3 mL: the temperature was taken along with the refractive index.

-The process was stopped when the refractive index was close to that of 0% cyclohexane and 100% toluene which was around 45 mL

Simple

The simple volume v. temperature graph, in comparison with the textbook image, was very similar. The shape is about the same in that it's almost linear and increases in temperature as the volume increases. The only difference in that graph is the starting temperature. In the ideal chart, the temperature starts at the boiling point of cyclohexane. In the graph presented above, the first notable distillate sample started a bit below the boiling point but quickly rose to the boiling point of cyclohexane and continued to rise steadily until about 105° C which is about 5° C below the toluene boiling point.

In the simple volume v. % cyclohexane graph in comparison with the literature graph, it was also almost exactly the same. Our group saw an outlier at 9 mL of distillate. This could be due to inadequate cleaning of the refractive index tool or contaminated equipment when setting aside the distillate. Otherwise, the graph matches the literature graph. It has a slight curve that reflects the increase in toluene in the solution as predicted. This graph was different from the textbook graph in that it didn't start at 100% cyclohexane in solution. The simple distillation rose in temperature quickly along with distillate making it so the starting % composition was around 65%

Fractional

The fractional volume v. temperature graph in comparison with the literature graph is very similar. They both experience a rise in temperature along with the volume of distillate taken. they both experience a bit of an increase towards the middle as the temperature spikes a bit along with the volume of distillate taken.

The fractional volume v. % cyclohexane graph in comparison with the literature graph is also very similar. They both have an "s" shape as they experience a decrease in cyclohexane with the volume of distillate taken. This decrease drops dramatically in the middle in both graphs as the % cyclohexane diminishes quickly at this point. After this, the two graphs continue on steadily. The literature graph and the graph presented above are both similar in shape and characteristics, properly displaying fractional distillation. The only part of the fractional distillation graph above that was not in comparison with the literature chart was the starting composition of cyclohexane. In this graph, it started at about 85% cyclohexane when it should've started to distillate with 100% cyclohexane in solution.

Through this lab, I learned a lot about distillation and the purification of a substance when in composition with another. One new laboratory technique I learned was the use of fractional distillation. I had never encountered fractional distillation before. It was interesting to see how it acted differently than simple distillation and presented differently within its graph. The dramatic decrease within the graph and purity of the distillate was interesting to see. A lab technique utilized that I had already known about was the use of refractive index and the tool we used to determine what it was for each solution. I'm very familiar with refractive indices for substances and I have used the same measuring tool in a different lab so it was unique to learn and utilize it in a new context. If I were to repeat the lab, I would let the solution in the round bottom flask boil a bit slower allowing cyclohexane, with the lower boiling point, to boil off first without a dramatic increase in temperature forcing some of the toluene to boil off early affecting the starting composition of the distillate.

1.   What would be the effect on the boiling point of a solution such as water if a non-volatile but soluble substance like salt was present? What if a non-volatile and insoluble substance like sand was present?

A soluble salt in the presence of water would increase its boiling point as it would separate into its respective ions, due to its non-polar composition, which contributes to a higher boiling point due to new attractions being formed with water. If an insoluble substance was present, there would be no change in the boiling point and instead a precipitate after boiling.

2.  Why would we not conduct distillations in a completely closed/sealed apparatus? 

A closed apparatus is not appropriate for distillation due to the vapor pressure accumulation which could build up unwanted pressure causing it to explode.

3.  How is fractional distillation as performed in the lab both the same and different from how it is performed at an oil refinery? You will need to look up information on the web how oil fractions are separated.  If you use google search, my suggestion is to choose images and then select a website that has a really nice visual image.

Fractional distillation performed in the lab and at an oil refinery are the same as they both collect products purified by the distillation process. They're different because the oil refinery collects multiple products at multiple stages by continuing to heat up the distillation and collect a product at different levels based on their respective boiling points. In the lab, only one product is being purified through the fractional distillation technique.