9.1-Manufacture of Sulphuric Acid

1) Uses of Sulphuric Acid

Sulphuric acid has many industrical uses. The major use of sulphuric acid is in the production of phosphate fertilizers.

2) Manufacture of sulphuric acid in industry

Sulphuric acid is manufactured in industry through Contact process. The raw materials for the manufacture of sulphuric acid in Contact process are

sulphur,oxygen and water. There are three stages in Contact process:

a)Stage 1:Combustion of sulphur(To produce sulphur dioxide gas)

-Molten sulphur is burnt in excess air to produce sulphur dioxide gas.S(l) + O2(g) → SO2(g)

-Sulphur dioxide gas is also produced by heating sulphide ores like iron persulphide, FeS2 in excess air.

4FeS2(s) + 11O2(g) → 2Fe2O3(s) + 8SO2(g)-The mixture is then purified,dried and cooled.

Uses of sulphuric

acid

Manufacture of dyes,pigment,

paints

Manufacture of artificial fibres

like rayon,nylon

Matallurgy: Cleaning materials

Manufacture of insecticides

As an electrolyte in car batteries

Leather tanning

Manufacture of detergents

Production of fertilisers

b)Stage 2:Oxidation of sulphur dioxide gas(To produce sulphur trioxide gas)

-Sulphur dioxide and excess oxygen gas are passed over Vanadium(V) oxide, V2O5

catalyst at 450C - 550C and pressure of 1 atmosphere.2SO2(g) + O2 ⇋ 2SO3(g)

△H = -197kJ mol-1

-99.5% of sulphur trioxide gas is produced via a reversible,exothermic reaction.-Basically, sulphur trioxide produced is contaminated with a by-product, sulphur dioxide gas. Thus, sulphur dioxide is absorbed with calcium hydroxide to prevent it from escaping to the air, causing environmental pollution.

c)Stage 3:Absorption of sulphuric acid(To produced liquid concentrated sulphuric acid)

-Sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum, H2S2O7.

SO3(g) + H2SO4(l) → H2S2O7(l) -The oleum is then diluted with water to produce liquid concentrated sulphuric acid.

SO3(g) + H2O(l) → 2H2SO4(aq)

Sulphur trioxide is not directly dissolved in water to form sulphuric acid.SO3(g) + H2O(l) → H2SO4(aq)

This is because the heat evolved in the reaction will vaporise the liquid sulphuric acid to a large cloud of sulphuric acid mist. The mist is corrosive, pollutes the air and is difficult to condense.

3) Environmental pollution by sulphur dioxide

Sulphur dioxide can cause environmental pollution. It is produced from:

a) the burning of sulphur in the Contact process.b) the extraction of metals from their sulphide ores.c) the burning of fossil fuels (petroleum,natural gas,coal).

Inhaling sulphur dioxide causes coughing, chest pain, shortness of breath, bronchitis and lung diseases.

When sulphur dioxide dissolves in rainwater, it forms sulphurous acid and causes acid rain.

SO2(g) + H2O(l) → H2SO3(aq) Sulphur dioxide can be oxidised to sulphur trioxide when:

a) reacted with nitrogen dioxide.SO2(g) + NO2(g) → SO3 (g) + NO(g)

b) catalysed by dust particles or water droplets.2SO2(g) + O2(g) ⇌ 2SO3(g)

The sulphur trioxide produced dissolves in rainwater; it forms sulphuric acid and causes acid rain.

SO3(g) + H2O(l) → H2SO4(aq) Acid rain produced may lead to the following effects:

a) Acid rain corrodes the buildings and statues made of limestone. Limestone reacts with sulphuric acid to form calcium sulphate.

CaCO3(s) + H2SO4(aq) → CaSO4(s) + CO2(g) + H2O(l)

b) Acid rain corrodes the metallic structures. Iron reacts with sulphuric acid to form iron (II) sulphate.

Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g)

c) Acid rain reduces the pH value of the soil as well as leaches out the minerals and nutrients in the land. Plants die of malnutrition and diseases, thus destroying the trees in forests.d) Acid rain increases the acidity of water in lakes and rivers. Aquatic organisms cannot survive in acidic water, thus causing the death of aquatic organisms.

Emission of sulphur dioxide gas during the Contact process can be removed by reacting the gas with:a) ammonia or ammonium hydroxide to produce ammonium sulphate (used as a fertilizer)b) calcium hydroxide or calcium carbonate to produce calcium sulphate (used in the manufacture of plaster and cement).

9.2-Manufacture of Ammonia and Its Salts

1) Uses of ammonia

Ammonia is a valuable source of nitrogen that is essential for the growth of plants. The major use of ammonia is in the production of nitrogenous fertilisers.

Ammonia is used in the manufacture of nitric acid via Ostwald process. There three stages in Ostwald process:

a)Stage 1:(To produce nitrogen monoxide gas)Ammonia is oxidised to form nitrogen monoxide and water.

4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(l) △H = -1170 kJ mol-1

b)Stage 2:(To produce nitrogen dioxide gas)Nitrogen monoxide reacts with excess oxygen to form nitrogen dioxide.

2NO(g) + O2(g) → 2NO2(g)c)Stage 3:(To produce liquid nitric acid)Nitrogen dioxide reacts with oxygen and water to form nitric acid.

4NO2(g) + O2(g) + 2H2O(l) → 4HNO3(aq)

Uses of ammonia

Manufacture of nitric acid

Making ammonium

chloride in dry cell

Manufacture of synthetic fibres

Manufacture of refrigerant

Manufacture of ammonium

nitrate explosives

Making household

cleaning agent

Production of ammonium

sulphate fertilisers

Manufacture of wood pulp, lacquer and

varnish

2) Properties of ammonia The physical properties of ammonia are as follows:

The chemical properties of ammonia:

a) It reacts with hydrogen chloride gas to form dense white fumes of ammonium chloride.

HCl(g) + NH3(g) → NH4Cl(s)

b) It neutralizes various acids to form ammonium salts.HNO3(aq) + NH3(aq) → NH4NO3(aq)

H2SO4(aq) + 2NH3(aq) → (NH4)2SO4(aq)

c) The hydroxide ions from the aqueous solution of ammonia react with metal ions to form precipitates of metal hydroxides.

NH3(aq) +H2O(l) ⇌ NH4+(aq) + OH-(aq)

Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)

d) It burns in oxygen but not in the air.4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g)

Properties of ammoniaAlkalineMiscible in waterLess dense than airColourless gasPungent smell

3) Manufacture of ammonia in industry

Haber process is an important industrial process in the manufacture of ammonia. The raw materials for the manufacture of ammonia in the Haber process are

hydrogen and nitrogen gases. Nitrogen gas is obtained from fractional distillation of liquefied air. Hydrogen gas is obtained from natural gas.

a) Methane, CH4 in natural gas reacts with steam in the presence of nickel catalyst at 700C.

CH4(g) + H2O(g) → CO(g) + 3H2(g)

b) Carbon monoxide in the mixture is then oxidised to carbon dioxide using steam and iron catalyst.

CO(g) + H2O(g) → CO2(g) + H2(g)

The ratio of 1 mole of nitrogen gas to 3 moles of hydrogen gas is passed through a reactor.

The mixture is compressed to a high pressure of 200 atmospheres at 450C - 550C and catalysed by iron to speed up the reaction.

N2(g) + 3H2(g) ⇌ 2NH3(g) △H = -180 kJ mol-1

Ammonia formed is liquefied and separated from the unreacted nitrogen and hydrogen gases. These gases are passed back into the reactor for further reaction.

About 98% of ammonia is produced in this reversible, exothermic reaction.

9.3 -Alloys

1) Alloys The atom of pure metals are packed together closely. This causes the metal to have

a hight density The forces of attraction between atoms (metallic bonds) are strong. More heat

energy is needed to overcome the metallic bond so that the atoms are further apart during the melting. This is why metals usually have hight melting point.

Heat energy can be transferred easily from one atom to the next by vibration. This make metal good conduct of heat.

The freely moving outermost electrons within the metal’s structure are able to conduct electricity. Metal are, therefore, good electrical conductors.

Since atoms of pure metal are of the same size, they are arranged orderly in a regular layered pattern. When a force is applied to metal, layer of atom slide easily over one another. This make pure metals soft, malleable and ductile.

Layer of atom slide

WHAT ARE ALLOYS?1. Pure metal are

usually too soft for most uses. They also have a low

resistance to corrosion. They rush and tarnish easily.

2. To improve the physical properties of metal, a small amount of another element (usually

metal) is added to form another an alloy.

3. An alloy is a mixture of

two or more metals (something

non- metal) in a specific

proportion. For example:a. Bronze (90% of copper and 10% of tin)b. Steel (99% of iron and 1% of carbon)

4. The purposes of making alloys include the following:a)Increase the strength

i. Pure iron is soft and vary malleable. When a small amount of carbon is added to iron, an alloy, steal is formed. The more carbon is added, the stronger the steel becomes.

ii. Pure aluminium is light but not strong. With a small amount of copper and magnesium are added to aluminium, a strong, light and durable alloy call duralumin is produced.

b) Improving the resistance to corrosioni. Iron rust easily but stainless steel which contains 80.6% of iron, 0.4% of

carbon, 18% of chromium and 1% of nickel does not rush. These properties make stainless steel suitable for making surgical instrument and cutlery.

ii. Pure copper tarnish easily. When zinc (30%) is added, the yellow alloy which is known as brass develops a high resistance to corrosion.

c)Enhancing the appearancei. Pewter, an alloy of tin (97%), antimony and copper is not only hard but also

has a more beautiful white silvery appearance.

Force

Metals are ductile

Force

The shape of the metal change

Matel are malleable

ii. When copper is mixed with nickel to form cupronickel, an alloy that has an attractive silvery, bright appearance is formed which is suitable for making coins.

Alloy Composition Properties UsesHigh carbon steel 99% iron

1% carbonStrong,hard and

high wear resistance Making of cutting

tools, hammers and chisels

Stainless steel 80.6% iron0.4% carbon

18%chromium1% nickel

Do not rust and tarnish, strong and

durable

Making of surgical instrument, knives forks and spoons

Brass 70% copper30% zinc

Hard, do not rust, bright appearance

Making of ornaments, electrical wiring and plug.

Bronze 90% copper10% tin

Hard, do not corrode easily and

durable

For casting bells, medals, swords and statues

Pewter 90% tin2.5% copper

0.5% antimony

Ductile and malleable, white

silvery appearance

Making of ornaments, souvenirs and mugs

Duralumin 95% aluminium4% copper

1%magnesium

Light, strong and durable

Making part of aircrafts and racing cars

Cupronickel 75%copper25%nickel

Attractive, silvery appearance, hard

and tough

Making of silver coins

Composition, properties and uses of alloys

The formation of alloy

9.4 -Synthetic Polymers

What are polymers?

Molecule that consist of a large number of small identical or similar units joined together repeatedly are called polymer.

The smaller molecules that make up the repeating unit in polymer are caller monomer.

The process of joining together a large number of monomers to form a long chain polymer is called polymerisation.

Polymer can be naturally occurring or man-made (synthetic). Natural polymer are found in plant and in animals for example of natural polymers are starch cellulose, protein and rubber.

Two type of polymerisation in producing synthetic polymer are additional polymerisation.

Double bonds between two carbon atoms usually undergo addition polymerisation.

Some Common Addition Polymers

Name(s) Formula Monomer Properties Uses

Polyethylenelow density (LDPE)

–(CH2-CH2)n–ethyleneCH2=CH2

soft, waxy solidfilm wrap, plastic bags

Polyethylenehigh density (HDPE)

–(CH2-CH2)n–ethyleneCH2=CH2

rigid, translucent solidelectrical insulationbottles, toys

Polypropylene(PP) different grades

–[CH2-CH(CH3)]n–

propyleneCH2=CHCH3

atactic: soft, elastic solidisotactic: hard, strong solid

similar to LDPEcarpet, upholstery

Poly(vinyl chloride)(PVC)

–(CH2-CHCl)n–vinyl chlorideCH2=CHCl

strong rigid solidpipes, siding, flooring

Poly(vinylidene chloride)(Saran A)

–(CH2-CCl2)n–vinylidene chlorideCH2=CCl2

dense, high-melting solid

seat covers, films

Polystyrene(PS)

–[CH2-CH(C6H5)]n–

styreneCH2=CHC6H5

hard, rigid, clear solidsoluble in organic

toys, cabinetspackaging (foamed)

solvents

Polyacrylonitrile(PAN, Orlon, Acrilan)

–(CH2-CHCN)n–acrylonitrileCH2=CHCN

high-melting solidsoluble in organic solvents

rugs, blanketsclothing

Polytetrafluoroethylene(PTFE, Teflon)

–(CF2-CF2)n–tetrafluoroethyleneCF2=CF2

resistant, smooth solidnon-stick surfaceselectrical insulation

Poly(methyl methacrylate)(PMMA, Lucite, Plexiglas)

–[CH2-C(CH3)CO2CH3]n–

methyl methacrylateCH2=C(CH3)CO2CH3

hard, transparent solidlighting covers, signsskylights

Poly(vinyl acetate)(PVAc)

–(CH2-CHOCOCH3)n–

vinyl acetateCH2=CHOCOCH3

soft, sticky solidlatex paints, adhesives

cis-Polyisoprenenatural rubber

–[CH2-CH=C(CH3)-CH2]n–

isopreneCH2=CH-C(CH3)=CH2

soft, sticky solidrequires vulcanizationfor practical use

Polychloroprene (cis + trans)(Neoprene)

–[CH2-CH=CCl-CH2]n–

chloropreneCH2=CH-CCl=CH2

tough, rubbery solidsynthetic rubberoil resistant

Uses of synthetic polymers

Synthetic polymers in daily life

1. Synthetic polymers have many advantages over other type of materials:

a. They are cheap, light-weight and translucent.b. They are easily coloured, easily moulded and shaped.c. They are non-corrosive, waterproof and good insulator.d. They are durable and long lasting because they are resistant to decay, rusting

and chemical attacks.2. There are disadvantage using synthetic polymer:

a. Most of the synthetic polymer are flammable. When a synthetic polymer material catches fire, poisonous fumes are produce causing air pollution.

b. Synthetic polymers are non-biodegradable. When there are discharge, they cause litter problem and pollute the environment.

c. Plastic container that are left aside in an open area collect rainwater which becomes the breeding ground for mosquitoes.

d. There are limitation in recycle have to be separated out as the addition of non-recyclable polymers in the mixture affect the properties of the recycled polymers.

9.5-The Uses of Glass and Ceramics

1) Glass

The major component of glass is silica or silicon dioxide, SiO2

The main characteristics of glass are:a)Hard but brittleb)Chemically inertc)Transparent and impermeable(non-porous)d)Withstand compressione)Good heat and electrical insulators

Type of glass Composition Properties UsesFused glass SiO2: 100% Transparent

High melting point Good heat insulator

Lens Telescope mirrors Laboratory

apparatusSoda-lime glass SiO2: 75%

Na2O:15%CaO: 9%

Other:1%

Low melting point, easily molded into desired shape and size

Low resistant to chemical attacks

Brittle

Drinking glass, bottles

Electric bulbs Window glass

Borosilicate glass SiO2: 78%B2O3: 12%Na2O: 5%CaO: 3%

Al2O3:2%

Resistant chemical attack and durable

High melting point Good insulator to heat

Cooking utensils Laboratory

glassware such as conical flaks and boiling tube

Lead crystal glass (flint glass)

SiO2: 70%Pbo/PbO2:20%

Na2O: 10%

High refractive index High density Attractive glittering

appearance

Lenses and prisms Decorative

glassware and art object

Imation jewellery

2) Ceramics Traditional silicate ceramics are made by heating aluminosilicate clay such as kaolin

to a very high temperature.

Ceramics have many special properties that make them one of the most useful materials in our everyday life. That:

a. Are hard, strong but brittleb. Have high melting point and remain stable at high temperature c. Are heat and electric instrumentd. Are resistant to corrosion and weare. Are chemically not reactivef. Do not readily deform under stress

Ceramic play important role in our daily life. They are uses as a. Construction materialsb. Decorative itemsc. Electrical insulator

Materials Melting point/ °C

Density/G cm-

3Elastic

modulus/ GPaHardness/

mohs

Oxide ceramicAlumina,AL2O3

Beryllia, BeOZirconia, ZiO

205425742710

3.973.015.68

380370210

988

Non-oxide ceramicsBoron carbide,B4C3

Silicon nitride, Si3, n4

23502830

1900

2.503.16

3.17

280400

310

99

9

MetalsAluminiumSteel

6601515

2.707.86

70205

35