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Chapter 9: Manufactured Substances in IndustryUnderstand the manufacture of sulphuric acid.Synthesize the manufacture of ammonia and its salt.Understand alloys.Uses of synthetic polymers.Apply the uses of glass and ceramics.Evaluate the uses of composite materials.Appreciate various synthetic industrial materials.SULPHURIC ACIDSulphuric acid is a highly corrosive strong mineral acid with the molecular formula H2SO4.Sulphuric acid is a diprotic acid.Sulphuric acid has a wide range of applications.

manufacturing fertilisermanufacturing detergentmanufacturing pesticidemanufacturing synthetic fibreas electrolyte in lead-acid accumulatorremoving metal oxidemanufacturing paint

Manufacture of Sulphuric acid in industrySulphuric acid, H2SO4 is manufactured in industry through Contact Process.The raw materials used are sulphur, air and waterThe Contact process consists of four stages.

Stage 1Molten sulphur is burnt in dry air to produce sulphur dioxide.The gas produced is then purified and cooled.S+O2SO2Sulphur dioxide can also be produced by burning metal sulphide such as lead(II) sulphide or zinc sulphide in dry air.2PbS+3O22PbO+2SO2

Stage 2In a converter, sulphur dioxide and excess oxygen are passed through vanadium(V) oxide.vanadium(V) oxide act as catalyst to expedite the process.The optimum condition for maximum amount of product are as follow:Temperature: 450 500 CPressure: 2 3 atmAbout 99.5% of the sulphur dioxide, SO2 is converted into sulphur trioxide, SO3 through this reversible reaction.

Stage 3Sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum H2S2O7.SO3+H2SO4H2S2O7

Stage 4The oleum, H2S2O7 is then diluted with water to produce concentrated sulphuric acid, H2SO4 in large quantities.H2S2O7+H2O2H2SO4

Environmental and health issue.Sulphur dioxide, SO2 is one of the by-products of the Contact Process. It is one of the source of environmental pollution.

Acid RainSulphur dioxide (SO2) is the pollutant primarily associated with acid rain.Acid rain occurs when pH of the rain is between 2.4 and 5.0. This is due to the reaction of sulphur dioxide, SO2 with rainwater.SO2+H2OH2SO3The negative effect of acid rains include:corrosion of concrete building and metal structure.corrosion of monuments and statues made from marblecauses erosion of top soil.killing aquatic life.

Health EffectsSO2 is an irritant when it is inhaled and at high concentrations may cause severe problems in asthmatics such as narrowing of the airways, known as bronchoconstriction.Asthmatics are considerably more sensitive to the effects of SO2 than other individuals.

Sources of SO2The principal source of SO2 is from the combustion of fossil fuels in domestic premises and more importantly, non-nuclear power stations.Other industrial processes such as manufacturing of sulphuric acid also contribute to the presence of SO2 in the air.AMMONIAAmmonia is a compound of nitrogen and hydrogen with the formula NH3.It is a colourless gas with a characteristic pungent smell.Ammonia is a very important compound in industry.Although in wide use, ammonia is both corrosive and hazardous.

Uses of Ammonia

manufacturing nitrogenous fertilisersas cooling agent in refrigeratorto prevent coagulation of latexas raw material to manufacture nitric acid (Ostwald process)to make explosiveas cleaning agent to remove grease

MANUFACTURING AMMONIA : Haber ProcessAmmonia is manufactured in industries through Haber Process.In Haber process, nitrogen gas, N2 from the air is mixed with hydrogen gas, H2 derived mainly from natural gas.The mixture is compressed to a high pressure of 200 atmosphere at a temperature of about 450C.Iron is used as catalyst to speed up the rate of reaction.Chemical equation below shows the reaction.N2 (g) + 3H2 (g) 2NH3 (g)About 98% of mixture are converted into ammonia, NH3.The unreacted nitrogen gas, N2 and hydrogen gas, H2 are recycled and passed back into the reactor together with the new source of nitrogen gas, N2, and hydrogen gas, H2.

Characteristics of ammoniaAmmonia gas can turn a moist red litmus paper to blue.As an alkali, ammonia can react with acid to form salt and water.Example:H2SO4(aq) + 2NH3(aq) (NH4)2SO4(aq)HNO3(aq) + NH3(aq) NH4NO3(aq)H3PO4(aq) + 3NH3(aq) (NH4)3PO4(aq)Ammonia dissolve into water to form ammonium and hydroxide ion.NH3 + H2O NH4+ + OH-The hydroxide ion can react with positive ions to form precipitate.Example:Mg2+ + 2OH- Mg(OH)2Fe2+ + 2OH- Fe(OH)2Al3+ + 3OH- Al(OH)2Test for AmmoniaAmmonia is the only common alkaline gas, so it can be identified with moist red litmus paper turning blue.Concentrated ammonia when reacts with concentrated hydrochloric acid produces white fume.Ammonia gas + Hydrogen chloride gas ammonium chlorideNH3 (g) + HCl (g) NH4ClProperties of ammoniaColourlessPungent smellLess dense than airVery soluble in waterAlkaline gasForm white fume with hydrogen chloride.ALLOYAn alloy is a mixture of two or more metals mixed in a certain percentage.Most pure metals are weak and soft. The properties of pure metals can be improved by making them into alloys.Alloys are made toincrease the hardness of metals.Example:Magnalium is made from aluminium and magnesium to improve the hardness of the pure metals but at the same time, maintaining their lightness.prevent the corrosion of metals.Stainless steel which can resist rusting is made by adding carbon, chromium and nickel to iron.improve the beauty and lustre of metals.Copper and antimony added to tin produces pewter, used to make decorative items.

When force is applied, layers of atoms in pure metalslide. So, metals areductile. There are empty space between the atoms. When it is knocked, the shape of the metal changes.

So, metals aremalleable.

Pure metalWeak and soft.-contain atoms of same size regular and orderly arrangement.

Examples of alloyExamples of copper base alloy areCupro-nickelBronzeBrassMost copper base alloy has shiny surface

Cupro-nickelComponent: Cu 75%, Ni 25%Applications: Coins

BronzeComponent: Cu 90%, Sn 10%Applications: Decorative items, medals, artwork, pots and pans

BrassComponent: Cu 70%, Zn 30%Applications: Decorative items, electrical appliances, musical instruments, bell, nails, screw, pots

Examples of iron base alloy aresteelstainless steelmanganese steelThe iron base alloys are usually very hard

Steel Component: Fe 99%, C 1%Applications: Vehicles, ships, bridges, buildings

Stainless steelComponent: Fe73%, Cr 18%, Ni 8%, C 1%Applications: Kitchen appliances, watches, machine parts, knives, forks, spoons

Manganese steelComponent: Fe 85%, Mn 13.8%, C 1.2%Applications: Helmet, spring

Examples of aluminium base alloy areDuraluminMagnalium

Aluminium has low density, hence the density of aluminium base alloy is also low.

DuraluminComponent: Al 95%, Cu 4%, Mg 1%Applications: Aeroplane parts, electric cables, racing bicycles

MagnaliumComponent: Al 70%, Mg 30%Applications: Tyre rim of racing cars, skeletal body of aeroplanes

Examples of tin base alloy arepewtersolderMost tin base alloy has shiny surface and low melting point.

PewterComponent:Sn 91%, Sb 7%, Cu 2%Applications:Decorative items, souvenirs

SolderComponent:Sn 50%, Pb 50%Applications:Welding and soldering work

POLYMERS Polymer is a large molecule that is in the form of a long chain with a high relative molecular mass (RMM).It is made up of many smaller units called monomers -- joined together through a process called polymerisation. Thus the monomer is actually the repetitive unit of a long polymer chain.There are two types of polymers:Natural polymersSynthetic polymers

Natural PolymersThese occur naturally in living things. Some examples of natural polymers are:Natural rubberProtein in meat, leather, silk, hair and furCarbohydrates in cellulose, starch and sugarNatural polymers are made up of carbon, hydrogen, nitrogen and oxygen.

Synthetic PolymersSynthetic polymer is a polymer that is manufactured in industry from chemical substances through the polymerisation process.Examples of synthetic polymers are:plasticssynthetic fibreselastomers-- elastic polymer / rubberThe two types of polymerisation are:polymerisation by additionpolymerisation by condensation

Polymerisation By addition: Polymerisation by addition involves monomers with >C = C< bonding, where the monomers join together to make a long chain without losing any simple molecules from it.

By condensation:Polymerisation by condensation involves the elimination of small molecules like water, methanol, ammonia or hydrogen chloride during the process. Examples of products of this process are terylene and nylon-66.

Examples of synthetic polymer PlasticsPlastics are light, strong and do not react with any chemical substances, like acids and alkalis.They can be made into many shapes and sizes.They are also good insulators of heat and electricity.

Examples of Plastics:1. Polythene (polyethylene)Structure

Monomer: EtheneProduced by polymerisation: Addition Uses: Plastic bags containers and cupsAdvantages: light and strong

2. Polyvinyl chloride or PVC (polychloroethene)Structure

Monomer: ChloroetheneProduced by polymerisation: AdditionUses: Raincoat, Pipes to insulate electric wiresAdvantages: can be coloured; heat resistant

3. Polystyrene (polyphenylethene)Structure

Monomer: PhenyletheneProduced by polymerisation: AdditionUses: Packaging materials, children toys, ball-point pens, as heat and electric insulatorsAdvantages: light and strong

4. Perspex (polymethyl 2-methyl propenoate)Structure

Monomer: Methyl-2-methylpropenoateProduced by polymerisation: AdditionUses: Aeroplane window panes, Lenses, car lamp coversAdvantages: light, strong, translucent, stable towards sunlight

5. PolypropeneStructure

Monomer: PropeneProduced by polymerisation: AdditionUses: Plastics, Bottles, plastic tables and chairsAdvantages: strong and light

6. Teflon (polytetrafluoroethene or PTFE)Structure

Monomer: TetrafluoroetheneProduced by polymerisation: AdditionUses: To make non-sticky pots and pansAdvantages: hard, can withstand high temperatures and corrosives chemicals

Synthetic RubberSynthetic rubber is an elastomer or polymer which regains its size original shape after being pulled or pressed. [Natural rubber is an elastomer too.]Examples of synthetic rubber are neoprene and styrene-butadiene(SBR).

1. NeopreneStructure

Monomer: ChloropreneProduced by polymerisation: AdditionUses: to make rubber gloves and to insulate electric wires.

2. Styrene-butadiene or SBRStructure

Monomer: Styrene and butan-1,3-dieneProduced by polymerisation: AdditionUses: to make tyres, soles of shoes and mechanical belts.

Synthetic FibreNylon and terylene are synthetic fibres which undergo the condensation polymerisation process.These fibres resemble natural fibres but more resistant to stress and chemicals, and more long-lasting. In both cases, water is eliminated during the polymerisation process.

1. NylonStructure

Monomer: Produced by polymerisation: CondensationUses: To make umbrellas, carpets, comb, curtains, nylon string and rope, socks, toothbrush and so on.

2. TeryleneStructure

Monomer: Produced by polymerisation: CondensationUses: To make fishing nets, clothes (quick-dry, non-iron), cassette and video tapes.

Issue in Using Synthetic PolymersSynthetic polymers have multiple uses in daily life because of the following properties:Light and strongRelatively cheapWithstand corrosion and chemical reactionWithstand action of waterNon-flammableCan be coloured easilyEasily mould to shapeSynthetic polymers are also used to replace natural polymers such as cotton, silk and rubber.

However, synthetic polymers cause environmental pollution.Most polymers are not biodegradable .The open burning of plastics gives rise to poisonous and acidic gases like carbon monoxide, hydrogen chloride and hydrogen cyanide.These are harmful to the environment as they cause acid rain.Burning of plastics can also produce carbon dioxide--- too much of this gas in the atmosphere leads to the `greenhouse effect'.

These problem can be overcome by the following ways:Recycling polymers: Plastics can be decomposed by heating them without oxygen at 700C. This process is called pyrolysis. The products of this process are then recycled into new products.

Inventing biodegradable polymers: Such polymers should be mixed with substances that can be decomposed by bacteria (to become biodegradable) or light (to become photodegradable).

Glass and CeramicsReferred to as transparent, shiny substance.The most important component of glass and ceramics is silica ( silicon(IV) dioxide, SiO2).Both glass and ceramic have the following properties:Hard and brittleDo not conduct heat electricityInactive towards chemical reactionsWeak when pressure is appliedCan be cleaned easily

GlassIt is a mixture of two or more types of metallic silicates but the main component is silicon(IV) dioxide.

Glass has the following properties:

Transparent and not porousInactive chemicallyCan be cleaned easilyGood insulators of heat and electricityHard but brittleCan withstand compression but not pressure

Soda lime,glassComposition: SiO2 70%, Na2O 15%, CaO 10%, Others 4%

Properties:Low melting point (700C)Moldable into shapesCheapBreakableCan withstand high heatUses: Glass containers, Glass panes, Mirrors, Lamps and bulbs, Plates and bowls BottlesMade by heating sand (silica) with lime stone and Na2CO3Lead glass (crystal)Composition: SiO2 70%, Na2O 20%, PbO 10%

Properties:High density and refractive indexGlittering surfaceSoftLow melting point (600C)Denser Uses: Containers for drinks and fruit, Decorative glass and lamps, Crystal glassware, Lenses for spectacles.Made by substituting lead oxide for calcium oxide.

Borosilicate glass (Pyrex)Composition: SiO2 80%, B2O3 13%, Na2O 4%, AI203 2%

Properties:Resistant to high heat and chemical reactionDoes not break easilyAllows infra-red rays but not ultra-violet raysUses: Glass apparatus in laboratories, Cooking utensilsFused silicate glassComposition: SiO2 99%, Other - 1%

Properties:High melting point (1700C)ExpensiveAllows ultraviolet light to pass throughDifficult to melt or mould into shape

Uses: Scientific apparatus like lenses on, spectrometer, Optical lenses, Laboratory apparatusCeramicsCeramic is a substance that is made from clay and hardened by heat in a furnace maintained at a high temperature.Clay is composed of aluminosilicate with sand and iron(III) oxide as impurities.Examples of ceramics includeTilesCementBricksporcelain

The differences between the properties of ceramics, metals and non-metals are given belowPropertyMetalsNon-metalsCeramicHardnessHard but malleable and ductileSoft and brittleHard but brittleDensityHighLowAverageMelting pointHighLowVery highResistance to heatHighLowVery highHeat andElectrical conductivityGoodconductorGoodinsulatorGoodinsulatorChemical reactionsCorrodesCorrodesStable, does not corrodeComparing Glass and Ceramic

New Uses of Glass and Ceramics

Photochromic Glass

Photochromic glass is very sensitive to light.It darkens in the presence of bright light and lightens when the amount of sunlight lessens.

Conductive Glass

Conducting glass is a type of glass which can conduct electricity. It is obtained by coating a thin layer of a conducting material around the glass, usually indium tin(IV) oxide.It is used in the making of Liquid Crystal Display (LCD)Car Engine Block

When clay is heated with magnesium oxide, the ceramic that is produced has a high resistance to heat.This material is used to build the engine blocks in cars as they can withstand high temperatures.

Superconductors

Superconductors are electrical conductors which have almost zero (0) electrical resistance. Therefore, this conductor minimises the loss of electrical energy through heat.Yttrium barium copper oxide is a type of ceramic superconductorSuperconductors are used to make magnets which are light but thousands of times stronger than the normal magnet.

Composite MaterialsComposite materials are substances which contain 2 or more materials that combine to produce new substances with different physical properties from the original substances.

Wood and bones are examples of natural composite materials. Wood consists of strong and flexible cellulose fibres surrounded and held together by stiffer material called lignin.Bone is made up of living cells in a matrix of collagen fibres and calcium salts. Reinforced ConcreteComponent: Concrete (cement, sand, stones), steel

Ordinary concrete is strong but heavy. Concrete pillars must be big to support the weight. They take up space and cannot withstand stress for example from earthquakes.Steel pillars are too expensive and can rust.Reinforced concrete, containing steel rods in the concrete pillars, can make them stronger and able to support larger loads. It also does not rust.

Optical FibreComponent: SiO2, Na2CO3, CaO

This is a fine transparent glass tube that is made of molten glass.In telecommunications, light has replaced electrons as the transmitter of signals. This light transmits signals through optical fibre.Optical fibre is also used in the medical field as laser to do operation , endoscope to examine the internal organs of patients

Photochromic GlassComponent: glass, AgCl (or AgBr

Photochromic glass is very sensitive to light.It darkens in the presence of bright light and lightens when the amount of sunlight lessens.FibreglassComponent: Fibreglass and polyster resin

Fibre glass is obtained by adding a polyester resin to molten glass. It cannot be compressed easily and is more tensile than the original materials.Fibre glass is light, withstands corrosion, can be cast into different shapes, is impervious to water, not very flammable, not brittle and stronger than even steel.It is used to make racquets, construction panels, electrical appliances, pipes, and water tanks.

SuperconductorComponent: Yttrium oxide (Y2O3), BaCO3, CuO

Superconductors are electrical conductors which have almost zero (0) electrical resistance. Therefore, this conductor minimises the loss of electrical energy through heat.Yttrium barium copper oxide is a type of ceramic superconductorSuperconductors are used to make magnets which are light but thousands of times stronger than the normal magnet and electrical generators.