Table 1: Data on Distillation Fractions
Please note that measurements should be estimated to the nearest 0.1 mm
Samples (simple)
Acetone peak
Peak width at half height w
1/2 in mm
#1 #2 #3
Peak area from printout
% composition
(calculated)
Peak retention time (printout)
Peak retention distance in mm
Butanone peak
Peak width at half height w
1/2 in mm
Peak area from printout
#4
% composition
(calculated)
Peak retention time (printout)
Peak retention distance in mm
Samples (fractional)
Acetone peak
Peak width at half height w
1/2 in mm
Peak area from printout
% composition
(calculated)
Peak retention time (printout)
#5 #6 #7
Peak retention distance in mm
Butanone peak
Peak width at half height w
1/2 in mm
Peak area from printout
% composition
(calculated)
Peak retention time (printout)
Peak retention distance in mm
Table 1b: Calculated parameters for simple and fractional distillation
Enrichment factor
 s
Enrichment factor
 f
Theoretical plates (n)
HETP in mm
#8

Table 2: Data on 50:50 Mixture with Varying GC Conditions
Column:
Column
Temperature:
Acetone peak:
Peak width at half height w
1/2
(mm)
Peak area from printout
Peak retention time
Nonpolar
Run #9
Polar
Run #10
Nonpolar
Run #11
Peak retention distance (mm)
Butanone peak:
Peak width at half height w
1/2
(mm)
Peak area from printout
Peak retention time
Peak retention distance (mm)
Table 3: GC Conditions and Comparison of column effectiveness
Column:
Column temperature
Nonpolar
Run #9
Polar
Run #10
Nonpolar
Run #11
Column packing
Gas flow rate
(mL/min)
Sample volume
(

L)
Attenuation setting
Resolution (R)
GC Theoretical plates (n
GC
)
GC - HETP
GC
Polar
Run #12
Polar
Run #12

Students must turn in individual reports for Unit 2.
This report will be due one week after completion of all experimentation. Use the standard lab report format outlined in your course handout and include the information given below.
Abstract and Introduction: Follow usual format
Purpose (under Intro section):
Part 1 compares the effectiveness of the two types of distillation.
Part 2 examines the effect of GC conditions on the quality of analysis.
Experimental section
Procedural details may be very brief (a short paragraph describing each distillation). Include a labeled figure of each of the two types of distillation setups.
Results section for Part 1:
Data:
1. Construct a plot of temperature (y axis) vs. volume (x axis) of distillate (in drops) for both the simple and the fractional distillation. Indicate where one fraction ends and the next begins (there should be 4 fractions for each distillation).
2. Use Table 1: Data on Distillation Fractions to present the results for the GC analysis of all
8 fractions from the simple & fractional distillations and the 50:50 mixture.
For each peak, record in the table the width at half height (w
1/2
) measured to the nearest 0.1 mm, the peak area obtained from the computer program, calculated % composition of each peak, the retention time of the peak, and the retention distance measured to the nearest 0.1 mm.
3. Chromatograms should be attached. You may attach photocopies if your partner has the originals. Be sure to get all of the data entered into your notebook
Calculations:
Consult the pages that follow for equations for these calculations.
1. Calculate mole % compositions for fractions 1 – 8 and report these in Table 1 under
% Compositions.
2. Using the % composition for your initial fraction from both simple (#1) and fractional (#5) distillations, calculate the enrichment factors (
 s
and
 f
) for both distillations. These represent the change in mole ratio of A/B before & after the first fraction is distilled out.
3. Using your
 s
and
 f
from (2), calculate the following parameters to evaluate the fractionating column. These all go in Table 1b.
a) the number of theoretical plates (n) b) the HETP of your fractional distillation column in mm.

Discussion section for Part 1:
This should be a well thought-out essay explaining the distillation curves, the compositions of the successive fractions, and the differences between simple and fractional distillation results.
Consider the following points in your discussion:

Compare the shapes of your distillation plots to those shown in Williamson, Fig. 5.8.
Does your data look like what’s expected for the two types of distillation?

Do the % compositions of successive fractions from both simple and fractional distillations support the observed changes in boiling temperature?

Consider your GC data. How well do calculated peak areas agree with integrated values?
Here, focus on the data you obtained on the polar GC column vs the nonpolar GC column at two different temperatures using your 50:50 acetone-butanone mixture. The purpose of making these runs is not to determine % composition, but to evaluate the effectiveness of both types of columns and also to compare the quality of chromatograms obtained at two different column temperatures. Learning to evaluate and choose appropriate conditions for the use of instrumentation is a critical skill in your development as a scientist!
Experimental:
Since the procedure for Part 2 consists of simply injecting samples into the GC, it's not necessary to describe the procedure; simply a brief description of the composition of the mixture.
Results for Part 2:
Data:
Complete Table 2: Data on 50:50 Mixture with Varying GC Conditions by making measurements of peak half width w
1/2
, and retention distance on your chromatograms to the nearest 0.1 mm. List also the retention times. Attach chromatograms to the report.
Table 3: GC conditions and Comparison of Column Effectiveness should list the conditions used to analyze samples 9 – 12.
Conditions to be recorded in the table:
 actual column temperature (from gauge)
 column packing
 gas flow rate in mL/min of He
 sample volume in microliters
 attenuation setting
Calculated parameters: Use the equations on the pages that follow to calculate and present the following parameters for each of your 4 column polarity/temperature combinations:
 resolution (R) of peaks calculated from retention distances
 average theoretical plates (n
GC
) for the GC column

HETP
GC
value for the GC column
Calculations: Show the equations you used and one sample calculation for each parameter listed.

Discussion for Part 2:
This should be a well thought-out evaluation of the effects of changing temperature and column polarity on the ability to resolve the two peaks and produce accurate data with respect to peak areas (i.e. is there a significant error in % composition assuming they should all be 50:50).
Questions (Parts 1 & 2):
1. Explain why the fractional distillation curve in Fig. 5.8 gives a lower initial distillate temperature and then a much sharper rise in boiling temperature of the distillate than you observe for a simple distillation.
2. Suppose to separate a liquid mixture, you were given 2 packed distillation columns, A and B with HETP values of 5 cm for A and 10 cm for B. Would there be any theoretical difference in the quality of separation achieved by the 2 columns? Explain.
3. When you observe a fractional distillation in progress, you see that some liquid runs back from the column packing down into the distillation pot. Explain what is happening to the composition of the mix in your distillation pot. Which parameter (calculated for this report) gave you a quantitative assessment of this effect?
4. Consider a mixture of benzene, C
6
H
6
, b.p. = 80 o C and acetone CH
3
(C=O)CH
3
, b.p. = 56 o C.
a) Which compound will emerge first on a non-polar column? On a polar column?
b) Which type of column would most likely give better resolution between the two peaks: polar or nonpolar?
c) What would be the likely effect on peak resolution if the column temperature were raised
by 20 o
C?
d) What peak parameter would be likely to change (e.g. peak height, retention time, etc.) if the carrier gas (He) flow rate is cut in half? Explain.
e) Suppose the mixture also included butanone, CH
3
CH
2
(C=O)CH
3
, b.p. = 80 o
C.
What is the likely order of peak elution on a nonpolar column?

CALCULATIONS FOR UNIT 2 LAB REPORT, PART 1 (DISTILLATION)
FROM THE G.C. DATA
D
R in mm or t
R
in minutes
Retention Time (t
R
):
Retention distance D
R
should be measured in (mm) for each peak: distance from time zero to peak maximum, measured to nearest 0.1 mm
Retention Time (t
Peak Area (P):
R
) will be given in the peak integration table under each chromatogram
P will be given in the peak integration table
Calculated % concentration (C) or mole %:
C a
= P a
P a
+ P b
+ …
P a
= acetone peak area
C
P b b
= P
P a b
+ P b
+ …
= butanone peak area

CALCULATIONS OF COLUMN PARAMETERS TO ASSESS THE EFFECTIVENESS
OF FRACTIONAL DISTILLATION
Enrichment Factor,

From a simple distillation:
 s
= n
A n
A
D
L
/ n
B
/ n
B
D
L where n
A
D /n
B
D = the ratio of the mole percents from the initial distillate of a simple distillation (here, run #1) and n
A
L
/n
B
L
= the ratio of the mole percents in the original pot liquid
From a fractional distillation:
 f
= n
A
D
/ n
B
D n
A
L
/ n
B
L where n
A
D
/n
B
D
= the ratio of the mole percents from the initial distillate of the fractional distillation (here, run #5)

is a measure of how effective the initial separation of A and B was
Calculation of theoretical plates (n) for a fractionating column:
 f
=
 s n+1 or n = (log
 f
/ log
 s
) - 1
Height equivalent of theoretical plate (HETP)
HETP = length of distillation column (mm)
theoretical plates, n

CALCULATIONS FOR UNIT
2 LAB REPORT, PART 2
(GC CONDITIONS)
D
R

D
R
D
R
Retention distance:
D
R
is the distance in mm from time zero to the peak maximum

D
R
is the difference in mm between peak maxima 1 and 2
Resolution, R:
R = 2

D
R
2 w
1/2
(1) + 2 w
1/2
(2)
=
 w
D
R
1/2
Where (1) and (2) refer to adjacent peaks
(1) + w
1/2
(2)
Theoretical Plates,
GC
: (Note that this is not the same equation you use to find the n of a fractional distillation column; this refers to the GC column itself.) n
GC
= 16 (D
R
/ 2 w
1/2
)
2
Calculate n
GC
for each peak in the chromatogram, then take the average and report the average in the table.
HETP:
HETP
GC
= column length n
GC
(average)
For the Gow-Mac GCs, the column length = 1220 mm