A 50:50 mixture of two unknown liquids will be purified using simple and fractional distillation

CHEM 2243 Distillation Virtual Experiment

Read the following articles and watch the videos

Fractional Distillation Video https://www.youtube.com/watch?v=NFdHEyq-1pA

Gas Chromatography:

https://www.technologynetworks.com/analysis/articles/gas-chromatography-how-a-gas-chromatography-machine-works-how-to-read-a-chromatograph-and-gcxgc-335168

https://www.khanacademy.org/science/class-11-chemistry-india/xfbb6cb8fc2bd00c8:in-in-organic-chemistry-some-basic-principles-and-techniques/xfbb6cb8fc2bd00c8:in-in-methods-of-purification-of-organic-compounds/v/gas-chromatography

Supplementary Info

https://www.thoughtco.com/definition-of-fractional-distillation-604421

https://byjus.com/chemistry/fractional-distillation/

MIT Videos on Distillation

https://www.youtube.com/watch?v=GtuMlWMajtw

Experiment: Purifying and Identifying Unknown Liquids

A 50:50 mixture of two unknown liquids will be purified using simple and fractional distillation. Gas chromatography will be used to analyze the distillate that is collected. The observed boiling points and gas chromatograms will be analyzed to determine the identity of the unknowns and identify which technique was the best for purifying the mixture.

Possible Unknowns

Compound Name

Boiling Point Range

Ethyl Acetate

77-78 oC

2-Butanone

80-81 oC

2-Propanol

82-83 oC

Ethyl Butyrate

120-121 oC

Butyl Acetate

126-127 oC

3-Methyl-1-butanol

131-132 oC

  1. The purification technique of distillation uses a difference in what physical property to separate liquids? (1 point)
  2. When is appropriate to use simple distillation to purify liquids? (1 point)
  3. What are the advantages and disadvantages of simple distillation? (1 point)
  4. In what situation is fractional distillation the preferred method of purification? (1 point)
  5. What are the advantages and disadvantages of fractional distillation? (1 point)

This is a gas chromatography chromatogram of the 50:50 mixture of the unknown compounds before distillation.

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  1. What are the retention times for each of unknown compounds? (1 point)

Lab Data that was collected when a 50:50 mixture of unknowns was separated using simple distillation:

Simple Distillation

The temperature was 76o C when the first drop of distillate was collected.

Liquid was collected and the temperature gradually rose to 124 o C.

Fraction 2 was taken when liquid was distilling at 124o C.

Fractional Distillation

The temperature was 77o C when the first drop of distillate was collected.

Liquid was collected until the temperature reached 78 o C, then the temperature dropped.

The temperature of the hot plate was increased and a second fraction of liquid was collected at 126 o C.

  1. Based on the boiling points observed when the fractions were collected, what is the identity of the unknown compound isolated in fraction 1? (1 point)
  2. Based on the boiling points observed when the fractions were collected, what is the identity of the unknown compound isolated in fraction 2? (1 point)

This is the gas chromatography chromatogram from the simple distillation.

Simple Distillation Fraction 1 GC Chromatogram

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  1. Using the boiling points of your unknowns, identify the peaks in the GC chromatogram. Explain your reasoning. (3 points)

Simple Distillation Fraction 2 GC Chromatogram

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  1. What is the major component of fraction 2 and is fraction 2 a single pure compound? (1 point)

Fractional Distillation Fraction 1 GC Chromatogram

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  1. What is the major component of fraction 1 and is fraction 1 a single pure compound? (1 point)

Fractional Distillation Fraction 2 GC Chromatogram

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  1. What is the major component of fraction 2 and is fraction 2 a single pure compound? (1 point)
  2. Did the fractional or simple distillation do a better job of purifying the unknowns? Explain your answer by discussing the observed temperatures and the gas chromatograms. (4 points)
  3. Describe how fractional distillation can better purify a mixture of liquids by discussing a liquid vapor phase diagram. Draw a liquid vapor phase diagram and use this in your answer. (2 points)
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