form 4 chemistry

8/6/2019 Form 4 Chemistry

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SULPHURIC ACID

(H4SO4)USES OF SULPHURIC ACID

1. Sulphuric acid is used to produce chemical fertilizer such as ammonium sulphate and

potassium sulphate, which are highly soluble in water and can be easily absorbed by

plant.2. The other uses of sulphuric acid are:

To manufacture detergent

To manufacture synthetic fibres (a type of polymer)

To manufacture paint pigment As an electrolyte in lead acid accumulators

To remove the metal oxide from metal surfaces before electroplating

MANUFACTURE OF SULPHURIC ACID

1. Sulphuric acid is manufactured in industry though Contact process

2. The raw materials used in the Contact process are sulphur, air and water.

3. The Contact process contain three stage

Stage 1 Production of sulphur dioxide gas, SO2 by burning of sulphur with air

S + O2 SO2

Stage 2 Conversation of sulphur dioxide to sulphur trioxide, SO3 in the following

conditions:

a) Temperature:450-500Cb) Pressure: 2-3 atmospheres

c) Catalyst: Vanadium(V) oxide

2SO2 + O2 2SO3

Stage 3 Two processes are involved here:i. Sulphur trioxide is dissolved in concentrated sulphuric acid to produce oleum, H2S2O7,

a viscous liquid

SO3 + H2SO4 H2S2O7

ii. Oleum is then diluted with water to produce concentrated sulphuric acid

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H2S2O7 + H2O 2H2SO4

4. Figure below shows the three stages in the making of sulphuric acid by the Contactprocess in industry

In the converter

2

Sulphur Oxygen

S + O2 SO2

SO2 + H2SO4 H2S2O7

H2S2O7 + H2O 2H2SO4

2SO + O22SO3

Temperature: 450-500C

Pressure: 2-3 atmospheresCatalyst: Vanadium(V) oxide

Oxygen

Unreacted

2% SO2 is

flowed backto converter

together with

oxygen

The Contact Process

Outline of Contact process


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SULPHUR DIOXIDE AND ENVIRONMENTAL POLLUTION

1. Sulphur dioxide is one of the by-products of Contact process. It is a colourless and

poisonous gas with a very pungent smell.

2. It is a poisonous and acidic gas that can cause environmental pollution. Inhalingsulphur dioxide can cause lung diseases.

3. Sulphur dioxide gas dissolves in atmospheric water to form sulphurous acid, H2SO3 and

sulphuric acid, H2SO4. The presence of these acids in rain water causes acid rain.4. The effects of acid rain are as follows:

Corrodes concrete buildings and metal structures

Destroys trees and plants in forests

Makes the soil acidic and hence unsuitable for growth of plants

Makes the water in lakes and rivers acidic and may destroy aquatic life

Acid rain and environmental pollution

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AMMONIA AND

ITS SALTS(NH3)

USES OF AMMONIA

1. It is a very important compound in the industry.

2. The uses are:

i. In the manufacture of chemical fertilizers such as ammonium sulphate,ammonia nitric, ammonia phosphate and urea.

ii. As a cooling agent in refrigerators

iii. To make nitric acid (in the Ostwald process)

iv. To make explosives (from nitric acid)v. To prevent the coagulation of latex (keep latex in the liquid form)

vi. To produce ammonium chloride which is used as the electrolyte in dry cells

PROPERTIES OF AMMONIA GAS

1. The physical properties of ammonia gas include the following:i. It colourless and has a pungent odour.

ii. It dissolves in water to produce a weak alkaliiii. It less dense then air.

2. Ammonia gas reacts with hydrogen chloride gas to form white fumes of ammonium

chloride (this is used as a test for ammonia gas)

NH3 + HCl NH4Cl

3. Ammonia is alkaline in property and reacts with dilute acids in neutralization to producesalts. For example:

2NH3 + H2SO4 (NH4)2SO4

4. Aqueous solutions of ammonia react with metal ions (except Na+ ion, K+ ion and Ca+

ion) to produce precipitate of metal hydroxides.

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MANUFACTURE OF AMMONIA IN INDUSTRY

1. Ammonia is manufacture on a large scale in industry through the Haber process

2. Nitrogen gas used is obtained form the fractional distillation of liquid air.

3. Hydrogen gas used is obtained from the reaction between steam and heated coke ornatural gas.

4. In the Haber process, one mole of nitrogen gas and three moles of hydrogen gas react to

produce ammonia gas in the following conditions:i. Temperature: 450-500C

ii. Pressure: 200-500 atmospheres

iii. Catalyst used: Iron fillings

N2 + 3H2 2NH3

5. The ammonia product is then cooled down as liquid. The unreacted nitrogen gas and

hydrogen gas are pumped back to the catalytic column to be reacted again

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The Haber Process


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AMMONIUM FERTILIZERS

1. Nitrogen is required in large amount by plant to make proteins which are necessary

for growth and cell repair.2. Most plant are not able to get a nitrogen supply directly from the air although it is

abundant in the air (78%). Plants can only absorb soluble nitrogen compounds fromsoil through their roots.

3. The nitrogen compounds are usually soluble nitric salt, ammonia and ammonia salt

which are manufacture as chemical fertilizer.

ALLOYSPURPOSE OF MAKING ALLOYS

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Nitrogen Hydrogen

N2 and H2 are mixed in the proportion of1:3

N2 + 3H2 2NH3

Temperature: 450-500C

Pressure: 200-500 atmospheres

Catalyst used: Iron fillings

Liquidammonia

In cooling chamberUnreacted N2 and

H2 gases

In the reactor chamber

Outline Of Habert process


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1. An alloy is a mixture of two or more elements with a certain fixed composition in

which the major component is a metal.

2. Pure metals are weak and soft. This is because:

A pure metal contains atom of the same size arranged in a regular and orderly

arrangement

The orderly arrangement of atoms enables the layers of atoms to slide over eachother easily when an external force is applied on them. This makes the metal ductile

(metals can be drawn to form long wires)

There exist empty spaces in the structures of pure metals. When hammered orpressed, groups of metal atoms may glide into new positions in these empty spaces.

This makes the metals malleable (metal can be made into different shapes or

pressed into thin sheets)3. In the process of alloying, foreign elements are added to molten metal. When

hardened, these atoms of foreign elements replace the positions of some of the original

metal atoms.4. In an alloy, these atoms of foreign elements disrupt the orderly arrangement of the

metal atoms and also fill up any empty spaces in the metal crystal structure5. Hence, the layers of metal atoms are prevented from sliding over each other easily.

6. This makes the alloy harder and stronger, less ductile and less malleable than puremetals.

7. There are three aims of alloying a pure metal:

To increase the hardness and strength of a metal

To prevent corrosion or rusting

To improve the appearance of the metal surfaces, with a better finish and lustre

Alloy Composition Properties UsesHigh carbon steel 99% iron

1% carbon

Strong, hard and

high wear resistance Making of cutting

tools, hammers and

chisels

Stainless steel 80.6% iron0.4% carbon

18%chromium

1% nickel

Do not rust andtarnish, strong and

durable

Making of surgicalinstrument, knives

forks and spoons

Brass 70% copper

30% zinc

Hard, do not rust,

bright appearance Making of

ornaments,

electrical wiring

and plug.Bronze 90% copper

10% tinHard, do not corrode

easily and durable For casting bells,

medals, swords

and statues

Pewter 90% tin

2.5% copper

0.5% antimony

Ductile and

malleable, white

silvery appearance

Making of

ornaments,

souvenirs and

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Force

Layer of atom slide

Metals are ductile

Force

The shape of the

metal change

Matel are malleable


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mugs

Duralumin 95% aluminium

4% copper

1%magnesium

Light, strong and

durable Making part of

aircrafts and racing

cars

Cupronickel 75%copper

25%nickel

Attractive, silvery

appearance, hard andtough

Making of silver

coins

Composition, properties and uses of alloys

The formation of alloy

SYNTHETICPOLYMERS

THE MEANING OF POLYMERS

1. Polymers are large molecules that consist of a large number of small identical or similar

units joined together repeatedly are called polymer.

2. The smaller molecules that make up the repeating unit in polymer are caller monomer.3. Polymerization is the chemical process by which the monomers are joined together to

form a big molecule known as a polymer.

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4. Polymer can be naturally occurring or man-made (synthetic). Natural polymers are

found in plant and in animals for example of natural polymers are starch cellulose,

protein and rubber.5. Two type of polymerisation in producing synthetic polymer are additional

polymerisation.

6. Double bonds between two carbon atoms usually undergo addition polymerisation.

Some Common Addition Polymers

Name(s) Formula Monomer Properties Uses

Polyethylene

low density

(LDPE)

(CH2-CH2)nethylene

CH2=CH2soft, waxy solid

film wrap,

plastic bags

Polyethylene

high density

(HDPE)

(CH2-CH2)nethyleneCH2=CH2

rigid, translucentsolid

electrical

insulation

bottles, toys

Polypropylene

(PP) different

grades

[CH2-

CH(CH3)]n

propylene

CH2=CHCH3

atactic: soft, elastic

solid

isotactic: hard,strong solid

similar to LDPE

carpet,

upholstery

Poly(vinyl

chloride)

(PVC)

(CH2-

CHCl)n

vinyl chloride

CH2=CHClstrong rigid solid

pipes, siding,

flooring

Poly(vinylidene

chloride)

(Saran A)

(CH2-

CCl2)n

vinylidene

chlorideCH2=CCl2

dense, high-melting

solidseat covers, films

Polystyrene

(PS)

[CH2-

CH(C6H5)]n

styrene

CH2=CHC6H5

hard, rigid, clear

solid

soluble in organicsolvents

toys, cabinets

packaging

(foamed)

Polyacrylonitrile

(PAN, Orlon,

Acrilan)

(CH2-

CHCN)n

acrylonitrile

CH2=CHCN

high-melting solidsoluble in organic

solvents

rugs, blankets

clothing

Polytetrafluoroethylene

(PTFE, Teflon)(CF2-CF2)n

tetrafluoroethyleneCF2=CF2

resistant, smoothsolid

non-stick

surfaceselectrical

insulation

Poly(methyl

methacrylate)

(PMMA, Lucite,Plexiglas)

[CH2-

C(CH3)CO2CH3]n

methyl

methacrylate

CH2=C(CH3)CO2CH3

hard, transparent

solid

lighting covers,

signsskylights

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Poly(vinyl acetate)

(PVAc)

(CH2-

CHOCOCH3)

n

vinyl acetate

CH2=CHOCOC

H3

soft, sticky solidlatex paints,

adhesives

cis-Polyisoprene

natural rubber

[CH2-

CH=C(CH3)-CH2]n

isoprene

CH2=CH-C(CH3)=CH2soft, sticky solid

requires

vulcanizationfor practical use

Polychloroprene

(cis + trans)

(Neoprene)

[CH2-

CH=CCl-

CH2]n

chloroprene

CH2=CH-

CCl=CH2

tough, rubbery

solid

synthetic rubber

oil resistant

Uses of synthetic polymers

ISSUES OF THE USE OF SYNTHETIC POLYMERS IN EVERYDAY LIFE

1. Synthetic polymers have been used widely to replace natural materials because of thefollowing advantages:

a. Cheap, light-weight and translucent.b. Easily coloured, easily moulded and shaped.

c. Non-corrosive, waterproof and good insulator.

d. Durable and long lasting because they are resistant to decay, rusting andchemical attacks.

2. The use of synthetic polymer, however results in environmental pollution problems

from the disposal of synthetic polymers because:

a. Burning of polymers release harmful gases that cause air pollution.b. Synthetic polymers are non-biodegradable (cannot be decomposed by bacteria or

other microorganisms).c. Plastic containers become breeding places for mosquitoes.d. Plastic items block drains and rivers, causing flash floods.

e. Small plastics swallowed by aquatic animals cause death.

3. Petroleum, the main source of raw materials for the making of synthetic polymers is a

non-renewable source

4. Methods to overcome these problems of polymers are:

Reduce, reuse and recycle synthetic polymers

Make biodegradable polymers

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GLASS AND

CERAMICSTHE MEANING OF GLASS AND CERAMICS

1. The main component of both glass and ceramics is silica or silicon dioxide, SiO2

2. Both glass and ceramic have the same following properties:

a. Hard but brittle.b. Poor conductors of heat and electricity

c. Resistant to corrosion.

d. Inert towards chemicalse. Easy to maintain.

3. The uses of glass and ceramics also depends on their differences as follows:

Glass is transparent whereas ceramic opaque

Ceramic has a higher melting point than glass.

4. The uses of glass depend on the composition and properties as shown below.

Type of glass Composition Properties Uses

Fused 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 intodesired shape and

size

Low resistant tochemical 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 asconical flaks and

boiling tube

Lead crystal glass

(flint glass)

SiO2: 70%

Pbo/PbO2:20%

Na2O: 10%

High refractiveindex

High density

Attractiveglittering

Lenses and prisms

Decorative

glassware and artobject

Imation jewellery

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appearance

5. Ceramics are made from clay, sand and feldspar. Clay consists of aluminosilicate. Anexample of clay is kaoline.

6. Some uses of ceramics in daily life are shown below.

Examples Uses

Bricks, tiles and cement As building materials

Porcelain Materials for vases, plates, bowls

Insulators in toasters and irons, spark plugs in

car engines

To make insulating parts in electrical

appliances

Microchips To make microchips in computers, radios andtelevisions

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Compositematerials

THE MEANING OF COMPOSITE MATERIALS

1. A composite material is a structural material formed by combining two or more

materials with different physical properties producing a complex mixture.2. A composite material has more superior properties than the original components used

to make up the composite material.

3. Composite materials are harder, stronger and lighter, more resistant to heat and

corrosion compared to their original components. Composite materials are also madefor specific purposes.

4. Some common composite materials are:

a. Reinforced concreteb.Superconductor

c. Fibre optic

d.Fibre glasse. Photochromic glass

REINFORCES CONCRETE

1. Concrete is hard, fireproof, waterproof, comparatively cheap and easy to maintain. It is

more important construction materials.

2. Steel is hard with high tensile strength but expensive and can corrode.

3. The reinforced concrete is a combination of concrete and steel.

SUPERCONDUCTOR

1. Metal such as copper and aluminum are good conductors of electricity, but 20% of the

electric energy is lost in the form of heat during transmission.2. Superconductors are materials that have no resistance to the flow of electricity at a

particular temperature. Hence, 100% electricity transmission is possible.

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3. One of the most dramatic properties of a superconductor is its ability to levitate a

magnet. Superconductor are used to build magnetically levitate high-speed train (at

about 552 km/h).4. Superconductors are used to make chips for smaller and faster supercomputer.

Superconductors also play an important role in high speed data processing in internet

communication.

FIBRE OPTIC

1. Fibre optic is a composite material that in used to transmit signals for light wave.

2. Fibre optic is used in

a. Telecommunicate where the telephone substation are liked by fibre optic cables.

b. Domestic cable television networkc. Closed circuit television security system.

3. Fibre optic also used in medical fields. It is used in a number of instruments which

enable the investigation for internal body part without having to perform surgery.

FIBRE GLASS

1. Fibre glass is glass in the form of fine threads. Molten gas is dropped onto a refractory

rating disc when the glass flies off the disc glass to form fibre.2. Fibre glass is strong than steel, do not burnt, stretch or rot, resistant to fire and water but

is brittle.

3. When fibre glass added to a plastic, a new composite material fibre glass reinforcesplastic is formed.

4. Fibre glass reinforces plastic has more superior properties than glass and plastic. It is

a. Extremely strongb. Light weigh

c. Resistant to fire and water

d. Can be molded, shaped and twisted

PHOTOCHROMIC GLASS

1. When 0.01 to 0.1% of silver chloride (a type of photochromic substances) and a smallamount of copper (II) chloride are added to molten silicon dioxide, photochromic glass

is formed.

2. The photochromic glass has special properties. It darkens when exposed to strongsunlight or ultraviolet.

3. Photochromic glass is suitable for making sunglasses.

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form 4 chemistry

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