CHE 311 "Fractional Distillation"

Your lab report should follow the format and consist of the following:

Title (be specific)

Your Name

Date

Section Number (CHE 311-0X)

1. Introduction:

• Purpose of Experiment
• Important theory and/or background material
• Structures and/or reactions
• Approproate references to literature (if necessary).

A brief introductory discussion, in your own words, of the physical principles involved in the distillation of a liquid.

2. Methods / Materials: Usually a simple list, but make sure it is accurate and complete.

3. Experimental Procedure:

• Describes the process in chronological order
• Explain all of the steps in the order they actually happened, NOT as they were supposed to happen.
• If you've done it correctly, another researcher should be able to duplicate your experiment.

Of particular importance in the interpretation of your observations is a comparison of the simple distillation of the mixture with the distillation of the same mixture through a fractionating column. A tabulation of temperature-volume data for each distillation serves as the basis for the construction of two graphs, one for the simple and one for the fractional distillation.

Some comment on the efficacy of the distillation using the column should be offered. For example, the data you obtained may have indicated that the fractions collected were mixtures, although of different composition than the original. Thus an ideal separation may not have been achieved because of deficiencies in the apparatus (or your technique?). Some recommendations about improvement of the fractionation assembly and conduct of the distillation are then in order. The primary purpose of the experiment was not a determination of the boiling points of the components, so do not dwell on the aspect of it.

4. Results and Discussion:

• Results are usually dominated by calculations, tables and figures; however, you still need to state all significant results explicitly in verbal form.
• Discussion focuses on a question of understanding, "what is the significance or meaning of the results?".

Make a table of the data you collected.

Attach a graph (neat and professional using the computer) of the still head temp. vs. volume collected for the simple distillation. On the same graph, plot the data for the fractional distillation in a different color.

Describe the results you obtained from the simple and fractional distillation. See if you can put into words the data that you collected and the resultant graph.

What conclusions can you make from the results of your experiment? Compare the two methods for efficacy. If you have an opinion, back it up with data. See previous page.

5. References and Post-Lab Questions:

a. What is Raoult’s Law?

b. What is Dalton’s Law?

c. Describe how Raoult’s and Dalton’s Laws relate to fractional distillation as a separation technique.

d. What’s the difference between a packed column and an unpacked column a fractional distillation?

e. What is a theoretical plate?

f. Using the figure provided, a temperature composition diagram for mixtures of two compounds, A & B.

(1) From the graph, what are the boiling points of pure A & pure B?

(2) For a mixture that contains 50 mole% A and 50 mole% B, what is the boiling point? What is the composition of the first distillate and if this distillate were to be condensed, what at temperature would it boil? What is the composition of the vapor at this temperature?

(3) For a boiling mixture at 60^oC, what is the composition of the vapor and the composition of the liquid?

g. At what point do you change receivers during a fractional distillation if you are trying to separate the components?

h. What observations during a simple distillation would cause you to redo the distillation using a fractionating column?

© Dr. Noel Sturm 2014