University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
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Page 1 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
QUESTION ONE (10 MARKS)
1.1 Why is air passed through the drying tower in the Contact Process?
(1)
1.2 In which section is the heat recovered in an industrial process furnace?
(1)
1.3 How are undissolved impurities removed from the phosphoric acid process?
(1)
1.4 What form of urea is not easily taken up by plants?
(1)
1.5 What are the end products from gasification and reforming?
(1)
1.6 Which Sasol process produces oxygenated products in high yields?
(1)
1.7 Which extraction technique is used to extract sodium?
(1)
1.8 Which process converts sulfides to oxides?
(1)
1.9 Give one example of a building block for hemicellulose.
(1)
Page 2 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
1.10 The process of bleaching pulp aims to remove two components from the pulp. Identify
them.
(1)
QUESTION TWO (15 MARKS)
2.1 Consider the flow diagram for the Contact Process given at the back of the examination
question paper and answer the questions that follow.
i) Identify the process parts labeled A to D of the overall process.
(4)
A–
B–
C–
D–
ii) Give the balanced equation that takes place in part labelled B.
(1½)
iii) Give the balanced equation that takes place in part labelled C.
(2)
Page 3 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
iv) Explain how the reaction that takes place in part labeled C is optimized to ensure
maximum product is produced.
(4½)
v) Identify one tail gas that may exit into the atmosphere at part labeled D.
(1)
vi) Explain, with the aid of two examples, how the effects of gaseous pollutants are reduced
in the Contact Process.
(2)
Page 4 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
QUESTION THREE (19 MARKS)
3.1 Explain the importance of carrying out an energy balance on a chemical plant process
and how energy balances are calculated.
(2)
3.2 Which form of phosphoric acid is used in detergents? Draw the chemical structure and
explain fully how it functions in a detergent.
(4)
Page 5 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
3.3 Give the decomposition reaction that occurs in the rectifying column of the urea
process.
(2)
3.4 Based on this reaction, in 3.3 above, describe in detail if any recycling is necessary in the
process of urea manufacture.
(2)
3.5 Explain how the cost of energy in a urea processing plant is reduced.
(2)
Page 6 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
3.6 A fertiliser plant has a capital investment of for R 2 million each from 12 investors. The
fertiliser plant expenses are as follows:
Phosphate rock
R 2 million
Sulfuric acid
R 2.9 million
Energy
R 0.5 million
Laboratory services
R 3 million
Transportation
R 1 million
Packaging
R 0.75 million
Return on capital and depreciation was set at 9 % and 10 % respectively. In the first year of
production, the plant experienced unusual growth which allowed it to run at 110 % capacity.
However, due to national loadshedding, the company switched to solar energy and hence
had its energy costs reduced by 3 %. Determine the price that a ton of fertiliser must be
sold at if at 100 % capacity, the company was expected to produce 50 000 of fertiliser.
(7)
Page 7 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
QUESTION FOUR (19 MARKS)
4.1 Name the two types of raw material used to produce ‘syn gas’ at Sasol.
(2)
4.2 Explain fully the process of coal gasification with the aid of a simplified diagram.
Indicate in your answer the overall reaction that occurs in this process and the use of the
main end product as well as the by-product.
(11)
Page 8 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
4.3 The following diagram shows the high temperature Fischer Tropsch (HTFT) process and
the low temperature Fischer Tropsch (LTFT) processes using a cobalt and iron catalysts.
Answer the following questions based on this diagram:
0.20
0.04
HTFT (iron fluidised bed, 340°C)
Mass fraction
0.15
0.03
LTFT (cobalt slurry phase, 220°C)
0.10
0.02
LTFT (iron slurry phase, 240°C)
0.05
0.01
0.00
0
0
5
10
15
20
25
30
35
40
45
Carbon number
i)
Which Fischer Tropsch process produces the highest amount of petrol?
ii)
Which Fischer Tropsch process produces the highest amount of ‘heavier components’? (1)
iii)
Compare and contrast the HTFT and LTFT process based on reaction conditions and endproducts produced.
(1)
(4)
Page 9 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
QUESTION FIVE (18½ MARKS)
5.1 The formation of mercury amalgam with gold is an extraction method that can be used
to extract gold. Explain, with the aid of a simple fully labeled diagram, how this process
works showing the formation of the mercury amalgam.
(4½)
5.2 Give the balanced equation for the roasting of a Zinc blende ore.
(2)
5.3 Give the balanced equation for the reduction of the zinc oxide formed in the above
equation.
(2)
5.4 Give the temperature at which the above reduction (in 5.3) occurs.
(½)
Page 10 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
5.4 Use the Ellingham diagram given below to explain the temperature at which the
reduction equation above (in 5.3 and 5.4) occurs as well as the reaction.
(2½)
Page 11 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
5.5 During the cyanidation process of gold extraction, a large amount of waste is produced.
Explain where this waste emanates from in that process, the contents of this waste and
what measures are taken to control its disposal.
(4)
5.6 The mine dust produced in the mining industry is also a huge problem in South Africa.
Explain what measures are being taken to reduce this solid waste and why this is proving to
be beneficial.
(3)
Page 12 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
QUESTION SIX (18½ MARKS)
6.1 Draw the repeating units for cellulose labeling the important linkage between two
monomer units.
(4)
6.2 Explain why cellulose is difficult to dissolve in most solvents.
(1½)
6.3 Explain any recycling that the Kraft pulping process undertakes.
(4)
Page 13 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
6.4 The acid bisulfite process uses a 5-stage bleaching process. Describe this bleaching
process giving details about the bleaching chemicals used as well as the function of each of
these bleaching chemicals.
(6½)
Page 14 of 15
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2015 Main Examination Session, APCH 221: Chemistry and Industry
6.5 Give the reaction that produces cellulose xanthate and one use for it.
(2½)
Page 15 of 15