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Worksheet 14.2
Chapter 14: Chemistry in industry and technology – fast
facts
C.1 Iron, steel and aluminium
 Iron is extracted from its ores hematite (Fe2O3) and magnetite (Fe3O4) in a blast furnace.

Iron ore, coke and limestone (CaCO3) are added and hot air is blown in from the bottom.

The coke burns to form carbon dioxide: C (s) + O2 (g)  CO2.

The heat produced in this reaction makes the calcium carbonate decompose to calcium oxide:
CaCO3 (s)  CaO (s) + CO2 (g).

The carbon monoxide reduces the iron(III) oxide as it rises up the furnace:
Fe2O3 (s) + 3CO (g)  2Fe (l) + 3CO2 (g).

The calcium oxide produced from the thermal decomposition of limestone reacts with silicon
dioxide and aluminium oxide’s impurities to form liquid slag of calcium silicate, CaSiO3, and
calcium aluminate, Ca (AlO2)2.



CaO (s) + SiO2 (s)  CaSiO3 (l)
CaO (s) + Al2O3 (s)  Ca (AlO2)2 (l)
The iron produced by the blast furnace contains about 4% of carbon, which makes it brittle. It is
converted into steel by the basic oxygen process (BOC):
 Oxygen is blown throw the molten iron, and small quantities of alloying elements such as
nickel and chromium are added.
 The oxygen combines with the unwanted non-metal impurities to form oxides which either
escape as gases: C (s) + O2 (g)  CO2 (g) S (s) + O2 (g)  SO2 (g), or combine with the lime
(CaO) (added to the converter) to form a slag of calcium phosphate, Ca3 (PO4)2, and calcium
silicate, CaSiO3.
 Oxides of silicon and phosphorus are also formed:
4P + 5O2  P4O10
Si + O2  SiO2
An alloy is a homogenous
mixture containing at least one
metal formed when liquid
metals are added together and
allowed to form a solid of
uniform composition.
The presence of other elements
makes it more difficult for
atoms to slip over each other
and makes the metal harder.
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

The properties of steel may be also be modified by three heat treatment processes:

Annealing, in which the metal is allowed to cool slowly to produce a soft malleable steel;

Quenching, in which very hot metal is rapidly cooled so that the high-temperature crystal
structure is retained, giving a hard, brittle steel;

Tempering, in which the quenched steel is reheated to achieve a hardness intermediate
between that achieved by annealing and quenching.
Aluminium is found in the mineral bauxite. Its extraction of aluminium involves three stages:

The mineral is treated with aqueous sodium hydroxide. The amphoteric nature of the
aluminium oxide allows it to be separated from other metal oxides as it dissolves.
Al2O3 (s) + 2OH– (aq) + 3H2O (l)  2Al (OH)4– (aq)

The purified aluminium oxide is dissolved in molten cryolite. This reduces the melting point
and so reduces the energy requirements of the process.

The molten mixture is electrolyzed.

Reactions at anode:
2 O2– (l)  O2 (g) + 4e–
C (s) + O2 (g)  CO2 (g)

Reactions at cathode
Al3 + (l) + 3e–  Al (l)

Aluminium has a high thermal and electrical conductivity, and a lower density than steel.

It can be made stronger by alloying with other metals such as copper and magnesium.

The production of both steel and aluminium consumes large amounts of energy, uses large
amounts of water and produces a large amount of solid waste and the greenhouse gas CO2.

Recycling can greatly reduce the environmental impact.
C.2 The oil industry
 Crude oil, a mixture of hydrocarbons, is one of the most important raw materials in the world
today.

It is a source of fuels and an important chemical feedstock for the production of polymers,
pharmaceuticals, dyes and solvents.

Petrol is a highly concentrated and convenient energy source for use in transport.

The burning of hydrocarbons produces environmental side effects such as smog and global
warming.
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
Crude oil will last longer if we conserve energy and recycle materials such as plastics.

It is the most convenient and economical option at the moment but alternative energy sources and
feedstocks may be developed.

There are three important types of cracking:

Thermal cracking; in which the very long chain alkanes are heated to a very high
temperature giving ethene as the major product.

Catalytic cracking; in which the alkane vapour is passed over a zeolite catalyst at a lower
temperature to give less ethene and more branch-chained hydrocarbons, which are excellent
fuels.

Steam cracking; in which the alkane vapour is mixed with steam before cracking, which
produces more aromatic hydrocarbons. The feedstock of ethane, butane and alkanes with
eight carbon atoms is preheated, vaporized and mixed with steam at 1250–1400°C.
C.3 Addition polymers
 Polymers, with different chemical compositions can be formed by changing the monomer.

Ethene can polymerize in two distinct processes.

LDP (Low Density Polyethene) is produced at high
temperature and very high pressure in the presence of a
free-radical initiator (small amounts of O2 or peroxides). It
is a branched-chain polymer with an irregular lattice. It
has a lower density and lower melting point than HDP.

HDP (High Density Polyethene) is produced at lower
pressure and temperature in the presence of Zeigler
catalysts (Al (C2H5)3 and TiCl4). It has very little
branching and forms a regular lattice. It has higher density
and a higher melting point than LDP.

The isotactic form has methyl groups arranged on one side.

It is used to make car bumpers and plastic toys, and can be
drawn into fibres to make clothes and carpets.
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
The atactic form has methyl groups which are randomly
orientated. It is softer and more flexible and used as a
sealant and in other waterproof coatings.

Pure PVC is quite rigid as it has strong intermolecular forces between its polar chains.

Plasticizer molecules fit in between and separate the
polymer chains. The resulting plastic is softer and more
flexible.

Expanded polystyrene is made by expansion moulding. A volatile hydrocarbon, such as pentane,
is placed in a mould and heated when styrene (phenylethene) polymerises.

It has a low density, is white, opaque and an excellent thermal insulator.
Advantages of polymer use:

Plastics are relative cheap.

They are relatively unreactive and have low
densities.

They are good electrical and thermal
insulators.

They are flexible and can be easily coloured
and moulded.
Disadvantages of polymer use:
 Addition polymers are all currently produced
from crude oil – a limited resource.

Many polymers are not biodegradable and so
are difficult to dispose of.
C.8 Condensation polymers
 Polyurethanes are produced by the combination of monomers with more than one isocyanate
group with monomers with more than one hydroxyl group.

Polyurethane foam is produced by adding a small amount of water to one of the monomers before
they are mixed together.

The water reacts with a small number of isocyanate groups to produce carbon dioxide.
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
Polyethylene terephthalate (PET) is formed when ethane-1,2-diol and benzene-1,4-dicarboxylic
acid (terephthalic acid) are heated.

A phenol–methanal polymer is made by adding acid or alkali to a mixture of the monomers.

The phenol and methanal react together to form a condensation polymer.

The reaction is more complex than the previous examples as a network structure is built up.

The polymer is very rigid due to the cross-linking between the chains.

Polyethylene is a conjugated polymer with alternate single and double bonds produced by the
addition polymerization of ethylene.

The trans isomer is a semiconductor.

The conductivity can be further increased by the addition of small amounts of oxidizing agents
such as iodine.

The iodine atom takes an electron from a π bond of the polymer, which leaves one carbon atom
with a positive charge and another with an unpaired electron. The positive charge stays fixed, but
the conjugated π system allows the single electron to pass along the chain.
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
Polyester fibres can be blended with other synthetic or natural fibres to produce materials with the
most desirable features of each.

Polyester fibres can also be combined with polyamides to make clothes which are more
comfortable and which hold dyes fast.
C.4 Catalysts
 Catalysts increase the rate of some reactions but they do not change the position of equilibrium.

A catalyst can’t make more of a product than would eventually be produced without it. It can
however act selectively when two or more competing reactions are possible with the same starting
materials, to produce more of the desired product by catalyzing only that reaction.

Heterogeneous catalysts are in different states to the reactants.

They are generally preferred in industrial processes as they can be easily removed by filtration
from the reaction mixture.

They are only effective on the surface.

Homogeneous catalysts are in the same state of matter as the reactants.

All the catalyst is exposed to the reactants.
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

Many catalysts are either transition metals or their compounds. Transition metals show two
properties which make them particularly effective.

They have variable oxidation states and are particularly effective catalysts in redox reactions.

They adsorb small molecules onto their surface and so provide a surface for the reactant
molecules to come together with the correct orientation.
The following factors should be considered when choosing a catalyst:

Selectivity (produce only the desired product);

Efficiency;

Ability to work under mild/severe conditions;

Environmental impact;

Problems caused by catalysts becoming poisoned by impurities.
C.9 Mechanisms in the organic chemicals industry
 Free radical mechanisms involved in the manufacture of LDPE:

Initiation

In the propagation steps, the R – O● free radicals attack an ethene molecule.

The free radicals are very reactive and will remove a hydrogen atom from another chain if an
appropriate collision occurs.
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
The free radical produced can react
with other ethene molecules as
before to form a side chain.

HDPE is produced by passing ethane through a hydrocarbon solvent at low temperatures (<100°C)
and pressures (<5 atm.).

An insoluble mixture of titanium (IV) chloride and an alkyl aluminium compound – known as a
Ziegler–Natta catalyst – acts as a heterogeneous catalyst.

It follows an ionic mechanism which involves heterolytic fission of the π bond of the alkene
double bond.
Ti (complex) —X + CH2 = CH2  Ti (complex) —CH2 —C + H2 + X–
Ti (complex) —CH2 —C + H2 + CH2 = CH2 → Ti (complex) —CH2 —CH2 —CH2 —C + H2
C.5 Fuel cells and rechargeable batteries
 The hydrogen oxygen fuel cell operates with either an acidic or alkaline electrolyte.
With an alkaline electrolyte
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With an acid electrolyte



The overall reaction is the sum of the oxidation and reduction half-reactions: 2H2 (g) + O2 (g) 
2H2O (l).
The lead acid battery is used for heavy power applications as it can deliver a high current for short
periods of time.
It relies on the ability of lead to exist in two oxidation states: + 2 and + 4, and the insolubility of
lead (II) sulphate: PbSO4.
Discharging a lead acid battery
The overall reaction is: Pb (s) + 2H2SO4 (aq) + PbO2 (s)  2PbSO4 (s) + 2H2O (l)
Charging a lead acid battery
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Charging a Nickel-Cadmium battery
Discharging a lithium ion battery

Fuel cells and rechargeable batteries are both ways of converting the chemical energy of an
exothermic reaction into electrical energy.

The main difference is that the reactions in rechargeable batteries have to be reversible.
C.6, C.11 Liquid crystals
 Liquid crystals are fluids that have physical properties (electrical, optical and elasticity) that are
dependent on molecular orientation relative to some fixed axis in the material.

Examples include graphite, cellulose and the solution extruded by a spider to form silk and DNA.

Liquid crystal materials may not always be in a liquid crystal phase.
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
Thermotropic liquid crystal materials are pure substances that show liquid crystal behaviour over a
temperature range between the solid and liquid states. The biphenyl nitriles are common examples.

Lyotropic liquid crystals are solutions that show the liquid crystal state at certain concentrations.
Examples include soap and water.
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
Soaps and detergents form lyotropic liquid crystals when they combine with water.


Liquid crystal displays (LCDs) are used in digital watches, calculators and laptops.

The orientation of the polar molecules can be controlled by the application of a small voltage
across a thin film of the material. Light and dark areas can be controlled by the applied voltage to a
grid of electrodes.

Pentylcyanophenyl is used in liquid crystal display devices as it has the following properties:

It is chemically stable.

The liquid-crystal phase is stable over a suitable range of
temperatures.

It is polar so can change its orientation when an electric
field is applied.

It responds to changes of voltage quickly; it has a fast
switching speed.

The biphenyl nitriles have nematic liquid crystal properties. The nitrile group makes the molecules
polar, which ensures that the intermolecular forces are strong enough to align in a common
direction.

The biphenyl groups make the molecules more rigid and rod-shaped.

The long alkane chain ensures that the molecules cannot
pack together so closely and so maintains the liquid
crystal state.

It is used in electronic devices as:

It is chemically stable.

It has a liquid crystal phase stable over a suitable range of temperatures.

It is polar, making it able to change its orientation when an electric field is applied.
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
It responds to changes of voltage quickly; it has a fast switching speed.

The workings of a twisted nematic liquid crystal:

Each pixel contains a liquid crystal sandwiched between two glass plates. The plates have
scratches at 90° to each other.

The molecules in contact with the glass line up with the scratches and form a twisted
arrangement between the plates due to intermolecular bonds.

In the ‘off’ state, the light passes
through the second polarizing
filter as the plane of polarization
rotates with the molecular
orientation as the light passes
through the cell.

When a small threshold voltage is
applied across the cell (the ‘on’
state) the polar liquid crystal
molecules now align with the
field and the twisted structure is
lost.

The plane-polarized light is no
longer rotated, and so no light is
transmitted and the cell appears
dark.

When the electric field is
turned off, the molecules
relax back to their twisted
state and the cell becomes
light again. Each cell
represents one dot or pixel
of the final image.

Kevlar® consists of a long chains lined up parallel to one another by hydrogen bonds between the
NH2 groups from one chain and the C = O groups from another.

Kevlar® has rigid rod-shaped molecules that can result in lyotropic behaviour.
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
It dissolves in concentrated H2SO4 as the hydrogen bonds break when the O and N atoms are
protonated.
C.7 Nanotechnology
 Nanotechnology involves research and technology development at the 1 nm to 100 nm range.

It creates and uses structures that have novel properties because of their small size and builds on
the ability to control or manipulate at atomic scale.

Physical techniques allow atoms to be manipulated and positioned to specific requirements.

Chemical techniques position atoms in molecules using chemical reactions.

Nanotubes are made from carbon hexagons (like a rolled round graphite sheet) with pentagons
needed to close the structure at the ends.

Single- or multiple-walled tubes, made from concentric nanotubes, can be formed.

Bundles of the tubes have high tensile strength as strong covalent bonding extends along the
nanotube.

As the behaviour of electrons depends on the length of the tube, some forms are conductors and
some are semiconductors. This is a typical nanoscale (quantum) effect.

The differences between the bulk
properties and the size-dependent
properties on the nanoscale should be
noted.

Concerns over the use of nanotechnology include:

Large-scale manufacture can carry the same risk of explosion as materials have small particle
size and large surface area.

Toxicity regulations are difficult as properties depend on the size of the particle.
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
There are unknown health effects, because new materials have new health risks.

Concern that the human immune system will be defenceless against particles on nanoscale.

Responsibilities of the industries.

Political issues, such as need for public education for informed debate and for public
involvement in policy discussions.
C.10 Silicon and photovoltaic cells
 In p-type semiconductors, electron holes in the crystal are created by introducing a small
percentage of a Group 3 element. In n-type semiconductors inclusion of a Group 5 element
provides extra electrons.

A photovoltaic cell typically includes sheets of n-type and p-type silicon in close contact.

When n-type and p-type semiconductors are placed
together, electrons in the narrow area near the junction
flow from the n-type to the p-type semiconductor, and fill
the positive holes. This process cannot continue
indefinitely because the electron exchange results in both
sides of the junction becoming charged and opposing
further exchanges.

When light of the correct energy shines on the cell, however, more free electrons and positive
holes are produced.

Electrons from the n-type conductor pass through the external circuit to fill the holes in the p-type
conductor.
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C.12 The chlor–alkali industry
The flowing mercury cell

Reaction at cathode:
Na + (aq) + e–  Na (amalgam)
The sodium amalgam passes into a separate chamber where it reacts with water:
2Na (amalgam) + H2O (l)  2NaOH (aq) + H2 (g)

Reaction at anode:
2Cl–  Cl2 (g) + 2e–

The membrane cell is replacing both the mercury cell and the diaphragm cell because it is cheaper
to construct and operate; it does not use the toxic materials mercury and asbestos; it produces
sodium hydroxide of higher purity than that of a diaphragm cell.

The membrane is made from a
polytetrafluoroethene (PTFE) or
Teflon®-based material.
The diaphragm and membrane cells
 Reaction at cathode
2H2O (l) + 4e–  4OH- (aq) + H2 (g)

Reaction at anode:
2Cl-  Cl2 (g) + 2e–
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Important uses of chlorine, sodium hydroxide, and hydrogen
Environmental impact of the mercury cell
 Mercury is considered to be one of the most dangerous of the metal pollutants.

It interferes with the behaviour of other ions in the body (Ca2 +, Mg2 +, or Zn2 + ) and causes serious
damage to the nerves and brain.

In Minamata disease, the central nervous system is affected by organo–mercury compounds,
which are able to damage proteins by forming strong covalent bonds to the sulfur atoms present in
the cysteine amino acid units.

Mercury also causes birth defects and inhibits growth.
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