9.1,9.2
TRANSCRIPT
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