CHEM UNIT 2
Separation Techniques and Analytic Methods
EOM Preview Exercise
2023
Section I - BASICS
a. Distinguish between ‘accuracy’ and ‘precision’ indicating which is more important and why. [4 marks]
b. Provide three (3) key characteristics of an ideal standard solution [3 marks]
c. Calculate the mean for the following masses obtained from a gravimetric process (recrystallization) [4 marks]
7.45 x 10-3 g
6.75 x 10-3 g
1.05 x 10-2 g
5.35 x 10-3 g
d. If the sample in part c contained 0.015 g of pure substance what is the % yield for each crystallite [5 marks]
e. Distinguish between ‘absorption’ and ‘transmission’ in spectroscopic methods [4 marks]
Section II – FINER DETAILS
The word bank/list below should be used as reference for the following questions
1.
3.
5.
7.
9.
11.
IR Spectroscopy
UV Spectroscopy
Mass Spectroscopy
Colorimetry
Calorimetry
Gravimetry
2.
4.
6.
8.
10.
12.
Paper Chromatography
Thin Layer Chromatography
High Pressure Liquid Chromatography
Fractional Distillation
Steam Distillation
Titration
13. Solvent Extraction
a. Indicate whether the processes above are examples of separation techniques or analytic methods. NOTE:
Some can be both or neither. [13 marks]
b. Provide a brief summary of the theory or mechanism (with relevant mathematical expressions as needed) for
processes 2, 3, 6 and 7 that would make them appropriate/viable for use in chemistry. [4 marks]
c.
Briefly describe one (1) real word application for processes 2, 5 and 10. 3 marks]
d. Briefly describe one (1) functional limitation for processes 1, 4, 8 and 12. [4 marks]
e. State which two (2) processes are most similar in concept and practice. [2 marks]
f.
Pair the processes from the word list above with the most related or relevant to the following names / terms /
scenarios below [15 marks]
Azeotropic
Retention time
Molar absorptivity constant (ε)
Filtration
Raoult’s Law
Solubility
Separation funnel
Boiling chip
Path length
Chromophore
Fragmentation
Bitumen
Partition coefficient (KD)
Desiccation
Cuvette
Vibration
Density
Methyl orange
Section III – PRACTICAL APPROACH
a. Outline the critical steps with reference to the appropriate materials and equipment needed to determine the
amount of water present in a sample of hydrated copper sulphate [10 marks]
b. Provide (2) possible sources of error for the procedure in part (a) and one (1) recommendation for
enhancement/improvement of the outlined method [5 marks]
Section IV – RANDOM BONUS(ES):
a. Which analytical method could be used to determine nutrient profiles in leafy vegetables? [1 mark]
b. Lettuce versus celery versus cabbage – which is the top/ultimate waste-man vegetable? Why? [1 mark]
c. What does back-titration and Dr. Whittaker’s father (Dr. M. Whittaker) have in common? [3 marks]