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Scheme of work – Cambridge International AS Level Physical Science (8780)
CHEMISTRY – SECTION III
Unit 4: Industrial processes
Recommended prior knowledge
Unit 1 (Theoretical Chemistry), Unit 2 (Physical Chemistry) and Unit 3 (Inorganic Chemistry) should have been studied before this unit. The unit builds on the ideas
of atomic and molecular structure and bonding developed in Unit 1, those concerning enthalpy changes, equilibrium, kinetics and redox developed in Unit 2, and the
chemistry of nitrogen and sulfur developed in Unit 3.
Context
This self-contained unit can be studied either before or after Unit 5 (Organic Chemistry).
Outline
The unit draws together the industrial aspects of the Inorganic part of the course. Concepts developed in Units 1 and 2 (see prior knowledge above) are applied to
industrial processes involving the extraction of iron, the production of steel, the extraction of aluminium, the purification of copper, the manufacture of ammonia, the
uses of ammonia, and compounds derived from it, and the production of sulfuric acid.
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
(i) describe the essential
reactions in the extraction of
iron from hematite
Students need to know that carbon reduction is widely used to extract
iron (as well as other metals, such as zinc, lead and copper) from metal
oxides; that ‘roasting’ in air may be used to convert ores into metal
oxides; that purified coal (coke) is used as the reductant; that basic
oxides, such as CaO from limestone, are used to remove acidic
impurities such as SiO2 and P4O10. The equations involved in the
reduction and in the removal of impurities need to be learned; i.e.
C(s) + O2(g) → CO2(g); C(s) + CO2(g) → 2CO(g); Fe2O3(s) + 3CO(g) →
2Fe(s) + 3CO2(g); Fe2O3(s) + 3C(g) → 2Fe(s) + 3CO(g); CaCO3(s) →
CaO(s) + CO2(g); CaO(s) + SiO2(s) → CaSiO3(s).
Chemistry for Advanced Level 20.3
(ii) describe the conversion of
Students need to know that solidified iron from the blast furnace contains
Candidates should be able to:
C11(a)
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Cambridge International AS Level Physical Science (8780)
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Syllabus ref
Learning objectives
iron into steel using
magnesium (to remove
sulfur), basic oxides and
oxygen in the BOS (basic
oxygen steelmaking) process
Suggested teaching activities
Learning resources
too much (about 5%) carbon and so is too brittle for use. Before
removing C, sulfur impurities are removed by adding magnesium, Mg(s)
+ S(s) → MgS(s), otherwise SO2(g) would be formed. The carbon
content is removed by blasting oxygen through the liquid iron. This
removes C as CO/CO2 and converts phosphorus impurities into P4O10.
This, together with any remaining SiO2, is removed by CaO; 6CaO(s) +
P4O10(s) → 2Ca3(PO4)2(s)
Students need to know that the addition of small quantities of other
elements to molten iron will produce steel alloys with differing properties.
(iii) understand that the properties
of iron may be changed by
the controlled use of additives
to form steel alloys
The addition of small, controlled, amounts of carbon (up to 0.5%) gives
malleable ‘mild steels’; the addition of larger amounts of carbon (up to
1.0%) gives a harder, more brittle steel. The single or combined addition
of metals such as vanadium, chromium, manganese and nickel gives a
wide range of steels with differing properties.
C11(b)
name the uses of mild steel (car
bodies and machinery) and
stainless steel (chemical plant
and cutlery)
An internet search would prove useful here.
C11(c)
explain, including the electrode
reactions, the industrial
processes of:
(i) the extraction of aluminium
from molten aluminium
oxide/cryolite
Students need to know the individual electrode half equations; the use of
cryolite to lower the melting point and to increase the conductivity of
Al2O3; the need for the continual replacement of the carbon anodes; and
the environmental aspects of CO and HF emissions. Emphasise that the
cost of the large quality of electricity used in the process is a major factor
in this process.
(ii) the electrolytic purification of
copper
Students need to know the individual electrode half equations; how the
separation of reactive, easily oxidised, metals (e.g. Zn) and less-reactive
metals (e.g. Ag) impurities is effected – the former dissolving, but not
plating the cathode, and the latter not dissolving at all, but forming anode
“sludge”. An experiment using a brass anode and a copper cathode can
be performed to show this.
describe the Haber process for
the manufacture of ammonia from
Students need to know the origins (methane, air and water) of the
hydrogen and nitrogen used in this process; the use of an iron-based
C11(d)
v2 2Y07
Cambridge AS Level Physical Science (8780)
Chemistry for Advanced Level 20.4
Advanced Chemistry 84-85
AS Level and A Level Chemistry 6a.2
Teaching AS Practical Skill 10, 11
Chemistry for Advanced Level 20.2
Advanced Chemistry 83
2
Syllabus ref
C11(e)
C11(f)
Learning objectives
Suggested teaching activities
Learning resources
its elements, giving essential
operating conditions, and
interpret these conditions
(qualitatively) in terms of the
principles of kinetics and
equilibria (see also Sections C5
and C6)
catalyst and the optimum reaction conditions employed (around 250 atm
and 400 °C). Consideration should be given to the theoretical optimum
conditions suggested by a Le Chatelier-based study of the formation of
ammonia.
For the Haber process, the idea of the temperature being a compromise
between the high rate but low equilibrium yield at high temperatures, and
low rate but high yield at low temperatures. Pressure is a compromise
between high yield and rate at high pressures, but at high capital and
running costs. The importance of recycling N2 + H2, so that a high yield
is not essential.
AS Level and A Level Chemistry 7a.7
understand the industrial
importance of ammonia and
nitrogen compounds obtained
from ammonia
Students should be aware of the use of ammonia as a fertiliser for acidic
soils; in the manufacture of nitric acid; its conversion into ammonium
nitrate, ammonium sulfate and urea, again for use as a fertiliser; the use
of ammonium nitrate in explosives; the formation of organic compounds
such as amines. An internet search would provide much information on
this topic.
Chemistry for Advanced Level 20.2
Advanced Chemistry 83
AS Level and A Level Chemistry 7a.7
Students need to know the SO2 is mainly obtained by the burning of
sulfur in air (some is obtained as a byproduct of the ‘roasting’ of sulfide
ores during metal extraction); that SO2 is mixed with more air and
passed over a V2O5 catalyst; that the SO3 produced is dissolved in 98%
sulfuric acid to form oleum, H2S2O7, to which water is then added.
Consideration should be given to the theoretical optimum conditions
suggested by a Le Chatelier-based study of the conversion of SO2 into
SO3.
Chemistry for Advanced Level 20.2
Advanced Chemistry 83
AS Level and A Level Chemistry 7a.7
describe the Contact process for
the manufacture of sulfuric acid
from SO2, giving essential
operating conditions, and
interpret these condition
(qualitatively) in terms of the
principles of kinetics and
equilibria (see also Section C5
and C6)
site 16 (manufacture of ammonia)
site 16 (manufacture of ammonia)
For the Contact process, the idea that the pressure is not as high as
might be expected, because the yield is high enough at low pressures,
which are much more economical and safe.
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