What is the percent composition of cyclohexane and toluene using the calculations in the picture? Toluene should be peaks A and B with integrations of 0.21 and 0.13 (unsure if you need to use them both) and cyclohexane is peak C with an integration of 1.00.
What is the percent composition of cyclohexane and toluene using the calculations in the picture? Toluene should be peaks A and B with integrations of 0.21 and 0.13 (unsure if you need to use them both) and cyclohexane is peak C with an integration of 1.00.
Principles of Instrumental Analysis
7th Edition
ISBN:9781305577213
Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Chapter5: Signals And Noise
Section: Chapter Questions
Problem 5.7QAP
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What is the percent composition of cyclohexane and toluene using the calculations in the picture? Toluene should be peaks A and B with integrations of 0.21 and 0.13 (unsure if you need to use them both) and cyclohexane is peak C with an integration of 1.00.
![Amplitude
10-
x104
8
4
2-
0
Data saved in "c:\projects\data\2023\02\20\70910"
12
10
8
Spectrum Scan [4/4]
4.5
1
A
A
0.21
ppm
4
2
6ST-
B
0.13
CO'T
START
6.77
1.88
1.19
END VALUE
5.97
0.21
1.33
0.13
0.36
1.00
-2](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4a38edaa-7cdb-4a66-939e-750a79ed49f3%2Fb0b9fba0-c8dc-4260-9296-c8b1393c6209%2Fqko7h4e_processed.jpeg&w=3840&q=75)
Transcribed Image Text:Amplitude
10-
x104
8
4
2-
0
Data saved in "c:\projects\data\2023\02\20\70910"
12
10
8
Spectrum Scan [4/4]
4.5
1
A
A
0.21
ppm
4
2
6ST-
B
0.13
CO'T
START
6.77
1.88
1.19
END VALUE
5.97
0.21
1.33
0.13
0.36
1.00
-2
Transcribed Image Text:Calculation of percent composition of compounds in a mixture, from proton NMR integration
values.
You can calculate the percent composition of compounds in a mixture from the NMR spectrum,
by analyzing the integration values of specific peaks that are characteristic of the compounds.
In the fractional distillation lab report you have two proton NMR spectra that contain both
cyclohexane and toluene:
For example, let us assume that:
The peak for the proton of cyclohexane integrates to 1.
The peak for the aromatic Hs of toluene integrates to 0.4
(you can choose another peak for toluene, as well)
One molecule of cyclohexane contains 12Hs. That means you have 1/12=0.083 molecules of
cyclohexane
One molecule of toluene contains 5 aromatic Hs. That means you have 0.4/5=0.08 molecules of
toluene.
The toluene content is smaller in mols (or molecules)
The ratio between mols of toluene/cyclohexane-(0.4/5)/(1/12).
If we multiply both ratios by 12, we find the mol ratio between toluene/cyclohexane=0.96/1.
Note: You should multiply by a factor that convert one of the components to 1 mol.
Multiplying by the MW of each compound will give you the ratio in grams, and mass percent
composition.
Toluene mass = 0.96 mols x 94.12 g/mol = 90.35 g
Cyclohexane mass = 1 mol x 84.16g/mol = 84.16 g/mol
% toluene = (90.35/(90.35+84.16)) x 100=51.8%
% cyclohexane = (84.16/(90.35+84.16)) x 100=48.2%
The sum of percent compositions must be equal to 1.
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