H6
Monitoring and Management in the Chemical Industry
Many chemists work in industries, monitoring and managing chemicals and chemical
reactions. The industrial synthesis of ammonia is an important application of an
equilibrium reaction and the chapter looks at the qualitative methods used to detect the
presence of anions and cations in samples.
Chemists in industry
Monitor and manage industrial processes to ensure
 Chemical reactions proceed efficiently in terms of speed
and yield
 The products are sufficiently pure and free from
dangerous contaminations
 The raw materials meet specifications.
 The work place remains safe and healthy
 Effluents and solid wastes from the factory meet statutory
requirements.
Uses of ammonia
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Haber-Bosch process
Industrial synthesis of ammonia
Fertilisers
Fibres and plastics
Nitric acid
Household cleaners
Detergents
N2(g) + 3H2(g)
2NH3(g)
The process is exothermic but has a slow rate of reaction at
room temperatures. The industrial conditions are a
compromise to achieve both an acceptable rate of reaction and
an acceptable yield. The conditions include
 A temperature of about 400oC
 Total pressure of about 250 atmospheres
 A magnetite (Fe3O4) catalyst.
Ammonia is drawn off from the reaction in a condenser and
the unreacted reactants are recycled.
Identification of
cations in solution
Cations in solution are primarily identified by precipitation
reactions.
Cations can be identified in solution containing only one
cation or in solutions containing a mixture of cations.
A flame test can also be used to identify cations in solution.
The presence of sodium ions in a solution can mask the
presence of other cations in a solution when a flame test is
used.
Pb2+
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Forms a white precipitate with ClForms a yellow precipitate with I-
Ba2+
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Forms a white precipitate with SO42No precipitate with OH- or FPale green flame test
Ca2+
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Forms a white precipitate with SO42Forms a white precipitate with FBrick-red flame test
Cu2+
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Pale blue solution
Forms a blue precipitate with OH- which dissolves in
ammonia to give a deep blue solution
Blue-green flame test
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Fe2+
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Pale green solution
White precipitate with OH- and this precipitate quickly
turns brown
Decolourises acidified potassium permanganate solution
Fe3+
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Yellow solution
Forms a brown precipitate with OHDeep red solution with SCN-
Identification of
anions in solution
Anions can be identified in solution by a variety of different
reactions, not just precipitation reactions.
CO32-
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Solution has a pH between 8 and 11
Bubbles of carbon dioxide gas produced when dilute
HNO3 is added
SO42-
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Forms a thick white precipitate with acidified Ba(NO3)2
Forms a white precipitate with acidified Pb(NO3)2
Cl-
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Forms white precipitate with AgNO3
Precipitate dissolves in ammonia solution
Precipitate darkens in sunlight
PO43-

Forms white precipitate with Ba(NO3)2 after the addition
of ammonia.
Forms a white precipitate with Mg2+ in an ammonia/
ammonium nitrate buffer.
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Flame colour of some
elements
Lithium
Sodium
Potassium
Calcium
Strontium
Barium
Copper
dull red
yellow
violet
brick-red
scarlet
lime-green
blue-green
Qualitative analysis
Determining the presence of substances such as
 Phosphate and nitrates in natural waterways
 Zinc and copper in natural systems
 Lead in the air and in surface soils
Quantitative analysis
Determining the amounts or concentrations of substances.
Traditional methods of quantitative analysis can be used to
determine the
 Percentage of sulfate in a lawn food
 Ammonium concentration in a fertiliser
 Ethanol concentration in wine
 Phosphate concentrations in detergent.
More sensitive methods of quantitative analysis are needed
and these methods include
 Atomic absorption spectroscopy
 Atomic emission spectroscopy