RHODES UNIVERSITY
Department of Chemistry
November 2021
Chemistry 201 Paper B
Time: 3.5 hours Marks: 90
Attachments: Chemical shift tables
Periodic Table and Physical Constants
Instructions: Attempt ALL questions.
Internal Examiners: Dr T. Geswindt Course coordinator
Dr X. Siwe Noundou
Dr A. May
Notes: Please (1) start each new question on a NEW PAGE.
(2) do NOT use red ink anywhere in your script.
(3) fill in the question numbers on the front cover of your answer
book in the order answered.
(4) Scan your pages in order and submit them as ONE document.
(5) Write your student number on each page.
This question paper consists of 7 pages including this cover sheet.
Please make sure that you have them all.
, Page 2 of 7 Chemistry 201B
November 2021
QUESTION 1
a) Briefly describe anodic stripping voltammetry (ASV). (3)
b) For the electrochemical cell represented below, the potential can be measured without drawing
substantial current:
reference electrode ∣ salt bridge ∣ analyte solution ∣ indicator electrode
Draw and label a typical cell of this type. Briefly describe each component. (13)
c) There are generally two types of interfacial electrochemical methods, namely potentiometric
methods and dynamic methods. What are the two types of electrochemical processes at the
electrode-solution interface that produce current? How do they differ? (4)
[20]
QUESTION 2
a) Discuss four limitations associated with pH measurement using the glass electrode. (8)
b) Which voltammetric technique is more sensitive between cyclic voltammetry and differential
pulse voltammetry? Why? (2)
[10]
QUESTION 3
Z A Name Spin Abund. Magnetogyric Recept rel Larmor Frequency
13
Ratio C 9.39798T
% [107rad s-1T-1] MHz
1 1 H Hydrogen ½ 99.9885 26.7522205 5.87E+3 400.13
1 2 D Deuterium 1 0.0115 4.10662914 6.52E-3 61.422
6 12 C Carbon 0 98.93 - - -
6 13 C Carbon ½ 1.07 6.728286 1.00E+0
7 14 N Nitrogen 1 99.636 1.9337798 5.90E+0 28.915
7 15 N Nitrogen ½ 0.364 -2.7126188 2.23E-2
8 16 O Oxygen 0 99.96 - -
a) With reference to the above table, answer the following questions:
(i) At what frequency will 13C resonate in a 9.39798T magnet? (2)
13 1
(ii) Why is C NMR a less sensitive spectroscopic technique than H NMR? (2)
(iii) Explain why the signal from Ha in [5]paracyclophane A appears at 6.54ppm while
that of Hb appears at 0.01ppm, in the 1H NMR spectrum. (3)
H2
C H2
H C
C
H2C Hb
CH2
a
H
A Question 3 continues over the page
Department of Chemistry
November 2021
Chemistry 201 Paper B
Time: 3.5 hours Marks: 90
Attachments: Chemical shift tables
Periodic Table and Physical Constants
Instructions: Attempt ALL questions.
Internal Examiners: Dr T. Geswindt Course coordinator
Dr X. Siwe Noundou
Dr A. May
Notes: Please (1) start each new question on a NEW PAGE.
(2) do NOT use red ink anywhere in your script.
(3) fill in the question numbers on the front cover of your answer
book in the order answered.
(4) Scan your pages in order and submit them as ONE document.
(5) Write your student number on each page.
This question paper consists of 7 pages including this cover sheet.
Please make sure that you have them all.
, Page 2 of 7 Chemistry 201B
November 2021
QUESTION 1
a) Briefly describe anodic stripping voltammetry (ASV). (3)
b) For the electrochemical cell represented below, the potential can be measured without drawing
substantial current:
reference electrode ∣ salt bridge ∣ analyte solution ∣ indicator electrode
Draw and label a typical cell of this type. Briefly describe each component. (13)
c) There are generally two types of interfacial electrochemical methods, namely potentiometric
methods and dynamic methods. What are the two types of electrochemical processes at the
electrode-solution interface that produce current? How do they differ? (4)
[20]
QUESTION 2
a) Discuss four limitations associated with pH measurement using the glass electrode. (8)
b) Which voltammetric technique is more sensitive between cyclic voltammetry and differential
pulse voltammetry? Why? (2)
[10]
QUESTION 3
Z A Name Spin Abund. Magnetogyric Recept rel Larmor Frequency
13
Ratio C 9.39798T
% [107rad s-1T-1] MHz
1 1 H Hydrogen ½ 99.9885 26.7522205 5.87E+3 400.13
1 2 D Deuterium 1 0.0115 4.10662914 6.52E-3 61.422
6 12 C Carbon 0 98.93 - - -
6 13 C Carbon ½ 1.07 6.728286 1.00E+0
7 14 N Nitrogen 1 99.636 1.9337798 5.90E+0 28.915
7 15 N Nitrogen ½ 0.364 -2.7126188 2.23E-2
8 16 O Oxygen 0 99.96 - -
a) With reference to the above table, answer the following questions:
(i) At what frequency will 13C resonate in a 9.39798T magnet? (2)
13 1
(ii) Why is C NMR a less sensitive spectroscopic technique than H NMR? (2)
(iii) Explain why the signal from Ha in [5]paracyclophane A appears at 6.54ppm while
that of Hb appears at 0.01ppm, in the 1H NMR spectrum. (3)
H2
C H2
H C
C
H2C Hb
CH2
a
H
A Question 3 continues over the page
