8/2/2019 chem 8 Lab 4

1/4

Giovanni Santangelo

Chemistry 8-L6

2-29-2012

1

Lab 4: Distillation

Introduction: The Lab is technique based and focuses on the ability to properly perform

distillation. Using the melting points the amount of gas distilled can be determined.

Physical Data Table:

Solvent Structure Chemical

formula

Weight

(g/mol)

Boiling

Point

(C)

Melting

Point

(C)

Density

g/cm3

MSDS

Cyclohexane C6H12 84.16

81-86 7 0.779 Skinirritant

flammabl

e

p-xylene C8H10 106.67

130-138 13.2 0.887 Harmfulto body

flammable

TolueneC7H8 92.14

104-111

-93 0.861 Skinirritant

flammabl

e

Procedure:

Assemble the distillation apparatus Transfer 30 mL into a 50 mL round bottom flask(both distillations) Heat until boiling point is achieved Collect 1 mL into a 10 mL graduated cylinder, transfer the 1mL to a test tube (cap

immediately).

Collect remaining 25 mL using a 25 mL graduated cylinder (do not collect to dryness) Collect last few drops in a test tube, cap immediately (do not collect to dryness) Follow procedure for gas chromatograph on cyclohexane sample Determine the mole fraction of cyclohexane

8/2/2019 chem 8 Lab 4

2/4

Giovanni Santangelo

Chemistry 8-L6

2-29-2012

2

Data & Observations:

Cyclohexane & Toluene Cyclohexane & P-xylene

mL Temperature (C) mL Temperature (C)

1 60 1 60

2 79 2 603 80 3 61

4 81 4 61

5 82 5 61

6 83 6 61

7 84 7 61

8 84 8 62

9 84 9 62

10 84 10 62

11 84 11 62

12 85 12 61

13 85 13 60

14 86 14 58

15 86 15 55

16 86 16 55

17 86 17 70

18 86 18 79

19 86 19 77

20 78 20 72

21 77 21 71

22 76 22 67

23 76 23 7824 78 24 84

25 79 25 82

0

20

40

60

80

100

0 5 10 15 20 25 30

Temp

erature

mL

Cyclohexane & Toluene

8/2/2019 chem 8 Lab 4

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Giovanni Santangelo

Chemistry 8-L6

2-29-2012

3

First mL:Area of Cyclohexane = 3252.70

Area of Toluene = 1055.47

Percent of Cyclohexane = 58.03%

Percent of Toluene = 18.83%

Last Drops:

Area of Cyclohexane = 79.97Area of Toluene = 5269.44

Percent of Cyclohexane = 1.49%

Percent of Toluene = 98.28%

Discussion:

In the lab we had to record the temperature every mL because when there was a spike in the

temperature the distillation then switched between cyclohexane and the other solution, either

toluene or p-xylene. There was little error in this lab and it went smoothly. My lab partner and I

had 4 peaks; however the Toluene and cyclohexane peaks were easily determined. However, in

the first drop which was collected the solution is mostly Cyclohexane because it has a lower

boiling point than that of Toluene.

Conclusion:

This experiment was successful in distilling the solutions separately. There was a clear line in my

data when the distillate switched between Cyclohexane and toluene/ p-xylene because the

temperature quickly jumped because the solutions other than cyclohexane had a higher boiling

point. My lab partner and I were successful in the gas chromatography and able to determine thepercent of solution in each sample. There was virtually no error, the only possible error may have

been not placing the test tube in the gas chromatography machine quick enough on the first mL.

Questions:

1. Yes the goals of this experiment were achieved because we were able to find how muchof each solution was in our sample using gas chromatography. At the lower boiling point

setting it consisted of mostly cyclohexane because it has a lower boiling point than

0

50

100

0 5 10 15 20 25 30

Temperature

mL

Cyclohexane & P-xylene

8/2/2019 chem 8 Lab 4

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Giovanni Santangelo

Chemistry 8-L6

2-29-2012

4

toluene, when all of the cyclohexane was gone the boiling point increased in order to

distill the rest of the toluene.

2. The second distillation was more efficient at separating the two components because theswitch in temperature between the cyclohexane and p-xylene was distinct. In the first

distillation, the temperature is similar and there is not a definitive jump so cyclohexaneand toluene did not separate as well. However, just looking at the cyclohexane and

toluene distillation the first mL had a better separation because the solution was mainly

cyclohexane, compared to the last few drops which was close between that ofcyclohexane and toluene. Adding a fractionating column would have helped the

separation of cyclohexane and toluene because fractional distillation has an extra columnbetween the flask and adapter, therefore it improves separation because there is more

time allowed for distillation to occur.

3. Distillation can be used for multiple things such as to separate and purify solutions. Oneexample is when you distill salt water in order to get pure water. The more distillation

done, the purer the solution will become. Also, the sample will become purer if fractional

distillation is used compared to simple distillation. As for the sample size, the larger thesample, the more time you need to distill in order to get the same purity as you would for

a smaller sample. With larger samples, it may be necessary to do multiple distillations in

order to get a pure sample.

4. Gas chromatography is a good technique to use to test purity of a solution and to separatea solution. However, it is not as effective as fractional distillation. Gas chromatography

works best on smaller sample sizes and can only be used on gases and liquids.

5. In the first mL we got 58% cyclohexane and 18% toluene. In the last few drops we got1.5% cyclohexane and 98% toluene. The percent recovery could have been improved if

we had used fractional distillation instead of simple distillation because there could have

been better distillation and improved separation. Also, using grease to assemble the

distillation equipment negatively affected my data because I got four peaks instead of justtwo.