22047806 Chemistry Form 4 Chapter 9

8/3/2019 22047806 Chemistry Form 4 Chapter 9

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9.1 SULPHURIC ACID

9.1.1 Properties of sulphuric acid

1. Sulphuric acid is a strong mineral acid.

2. Its molecular formula is H2SO4.

3. It is soluble in water.

4. Sulphuric acid is a non-volatile diprotic acid.

5. It is a highly corrosive, dense and oily liquid.

6. Concentrated sulphuric acid is a viscous colourless liquid.

Figure 9.2 Properties of sulphuric acid

Figure 9.1 A molecule of

sulphuric acid.

Properties of

sulphuric acid

Non-volatile

acid

Diprotic

acid

Soluble inwater

Highly

corrosive

Oily

liquidViscous

colourless

liquid

Dense
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9.1.2 The uses of sulphuric acid

(1) To manufacture fertilisers

There are many fertilizers that can be made of sulphuric acid. Some of them are:

a) Calcium dihydrogen phosphate (superphosphate)

b) Ammonium sulphate

c) Potassium sulphate

(2) To manufacture detergents

Sulphuric acid reacts with hydrocarbon to produce sulphonic acid. Sulphonic acid

is then neutralized with sodium hydroxide to produce detergents. Examples of

hydrocarbon

(3) To manufacture synthetic fibres

Synthetic fibres are polymers ( long chain molecules). Rayon is an example of a

synthetic fibre that is produced from the action of sulphuric acid on cellulose.

(4) To manufacture paint pigments

The white pigment in paint is usually barium sulphate, BaSO4. The neutralization

2

2 H2SO4

+ Ca3(PO

4)

2 Ca(H

2PO

4)

2+ 2CaSO

4

sulphuric acid + tricalcium phosphate calcium dihydrogen phosphate

H2SO4+2NH

3 (NH

4)

2SO

4

sulphuric acid + aqueous ammonia ammonium sulphate

H2SO4+2NH

3 (NH

4)

2SO

4

sulphuric acid + aqueous ammonia

ammonium sulphate
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As an acid

2%

Fertilisers

32%

Other

chemicals

16%

Paint pigment

15%

Detergents

12%

As an

electrolyte

10%

Synthetic

fibres

9%

Metal cleaning

2%Dyes

2%

of sulphuric acid and barium hydroxide produces barium sulphate.

(5) As an electrolyte in lead-acid accumulators

(6) To remove metal oxides from metal surfaces before electroplating

(7) To manufacture pesticides

(8) The uses of sulphuric acid in school laboratories are:

a. As a strong acid

b. As a drying or dehydrating agent

c. As an oxidising agent

d. As a sulphonating agent

e. As a catalyst

Figure 9.4 Uses of sulphuric acid in industry

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9.1.3 The industrial process in manufacture sulphuric acid

1. Sulphuric acid is manufactured by the Contact process.

2. Sulphuric acid is produced from sulfur, oxygen and watervia the contact

process.

3. The Contact process involves three stages.

4. Stage I: Production of sulphur dioxide gas, SO2.

This can be done by two methods,

a) Bur ning of sulphur in dry air in the furnace.

b) Burning of metal sulphide such as zinc sulphide in dry air.

5. Stage II: Conversion of sulphur dioxide to sulphur trioxide , SO3.

This is then oxidised to sulfur trioxide under the following conditions:

a) The presence of a vanadium(V) oxide , V2O5 , as a catalyst.

b) A temperature of between 450C to 550C.

c) A pressure of one atmosphere.

4

Sulphur Sulphur dioxide Sulphur trioxide Sulphuricacid

I II III

S+ O2

SO2

2ZnS + 3O2 2SO2 +

2ZnO

2 SO2

+ O2

2 SO3
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6. Stage III: Production of sulphuric acid

a) Sulphur trioxide is dissolved in concentrated sulphuric acid, H2SO4 to

produce oleum , H2S2O7

b) Oleum is reacted with water to form concentrated H2SO4.

7. In stage II,sulphur dioxide is dried first before being added to dry air to

produce sulphur trioxide. This is:

(a) To remove water vapour

(b) To remove contaminants

8. In stage III, sulphur trioxide is not dissolved directly in water to produce

sulphuric acid. This is because:

(a) sulphur trioxide has low solubility in water

(b) sulphur trioxide reacts violently and mists are formed instead of a liquid

5

H2SO

4+ SO

3

H2S

2O

7+ H

2O 2

H2SO

4
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burned in air

a) the presence of a vanadium(V) oxide as a catalyst.

b) a temperature of between 450C to 550C.

c) a pressure of one atmosphere

dissolved in sulphuric acid, H2SO4

diluted with equal volume of water H2O

Figure 9.5 Flowchart ofContact process

6

Sulphur or metal sulphide

Sulphur dioxide, SO2

Sulphur trioxide, SO3

Oleum, H2S

2O

7

Concentrated sulphuric acid H2SO4
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9.1.4 Environmental pollution by sulphuric acid

1. Sulphur dioxide is the main by- product produced when sulfur-containing

fuels such as coal or oil are burned.

2. Sulphuric acid is formed by atmospheric oxidation ofsulphur dioxide in the

presence ofwater. It also produces sulphurous acid.

3. Sulphuric acid and sulphurous acid are constituents ofacid rain.

4. Acid rain can cause many effects such as:

i. Corrodes concrete buildings and metal structureii. Destroys trees and plants

iii. Decrease the pH of the soil and make it become acidic

iv. Acid rain flows into the rivers and increases the acidity of water and kill

aquatic living things.

5. Hence, we must reduce the sulphur dioxide from the atmosphere by:

i. Use low sulphur fuels to reduce the emission of sulphur dioxide in exhaust

gases

ii. Remove sulphur dioxide from waste air by treating it with calcium

carbonated before it is released.

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9.2 AMMONIA AND ITS SALT

9.2.1 Properties of ammonia

1. A colorless, pungent gas.

2. Its molecular formula is NH3

3. It is extremely soluble in water.

4. It is a weak alkali.

5. It is about one half as dense as air

6. It reacts with hydrogen chloride gas to producewhite fumes of ammonium chloride.

7. Ammonia is alkaline in property and reacts with dilute acids in

neutralization to produce salts. For examples:

8.Aqueous solutions of ammonia produces OH ions (except Na+ ion, K+ ion,

and Ca 2+ ion) forming metal hydroxides precipitate.

8

NH3

+ HCl NH4Cl

2NH3

+ H2SO4

(NH4)

2SO

4

NH3

+ HNO3

NH4NO

3

Fe3+ + 3OH Fe(OH)

3

Brownprecipitate

Mg2+ + 2OH Mg(OH)

2

Whiteprecipitate

Figure 9.6 A molecule of

ammonia.
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Properties of ammonia

ColorlessPungent

smell

Extremely

soluble in

water

Weak

alkali

9. Some metal hydroxides such as zinc hydroxide and copper (II) hydroxide

dissolves in excess aqueous ammonia to form complexes.

Figure 9.7 Properties of ammonia

9.2.2 The uses of ammonia

9

Zn(OH)2

+ 4NH3 [Zn(NH

3)

4]2+ +

2OH

Cu(OH)2 + 4NH3 [Cu(NH3)4]2+

+ 2OH
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1. The major use of ammonia and its compounds is as fertilizers.

2. Ammonia is also used for the synthesis of nitric acid.

3. Ammonium fertilizers contain ammonium ions, NH4+, that can be

converted into nitrate ions by bacteria living in the soil.

4. Nitrogen is absorbed by plants to produce protein in the form of nitrates,

NO3, which are soluble in water.

5. The effectiveness of ammonium fertilizers is determined by the percentage

of nitrogen by mass in them. The fertilizer with a higher percentage of nitrogen is

more effective.

6. The percentage of nitrogen by mass can be calculated using this formula:

9.2.3 The industrial process in manufacture of ammonia

1. Haber process is the industrial method of producing ammonia.

2. It needs direct combination of nitrogen and hydrogen under high pressure in the

presence of a catalyst, often iron.

3. Nitrogen gas used in Haber process is obtained from the frictional distillation of

liquid air.

4. Hydrogen gas used in Haber process can be obtained by two methods:

a) The reaction between steam and heated coke (carbon)

b) The reaction between steam and natural gas ( consisting mainly of

methane)

5. In the Haber process:

10

C + H

2O CO +

H2

CH

4+ 2H

2O CO

2+

4H2

Mass

of nitrogen

X 100%

Molar mass offertilizers
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a) A mixture consisting of one volume of nitrogen gas and three volume of

hydrogen gas is compressed to a pressure between 200 500 atmospheres.

b) The gas mixture is passed through a catalyst of powdered iron at a

temperature of 450 - 550C.

c) At this optimum temperature and pressure, ammonia gas is produced.

9.3 ALLOYS

11

N2+ 3H

2 2NH

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9.3.1 Physical properties of pure metals

1. Pure metals have the following physical properties :

a)Good conductor of electricity

b)Malleable

c) Ductile

d)High melting and boiling point

e)High density

2. Pure metals are weak and soft because the arrangement of atoms in pyre

metals make them ductile and malleable.

a) A pure metal contains atoms of the same size arranged in a

regular and organized closed-packed structure.

b) Pure metals are soft because the orderly arrangement of atomsenables the layers of atoms to slide over each other easily when an

external force is applied on them. This makes the matels ductile and

metals can be drawn to form long wires.

c) There are imperfections in the natural arrangements of metal

atoms. Empty space exist in the structures of pure metals. When

hammered or pressed, groups of metal atoms may slide into new

positions in the empty spaces. This makes metals malleable, able to be

made into different shapes or pressed into thin sheets.

3. The strong forces of attraction between metal atoms requires high energy

to overcome it. Hence, most metals have high melting points.

4. The close-packed arrangement of metal atoms results in the high density

of metals.

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Properties of

metals

Good conductor of electricity

Ductile

High melting and boiling point

Malleable

High density

Figure 9.8 Properties of metals

9.3.2 Meaning and purpose of making alloys

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

in which the major component is a metal.

2. in the process of alloying, one or more foreign elements are added to a

molten metal. When the alloy hardens, the positions of some of the metal

atoms are replaced by the atoms of foreign elements, which size may be

bigger or smaller than the original metal atoms.

3. In an alloy, these atoms of foreign elements disrupt the orderly

arrangement of the metal atoms and also fill up any empty space in the

metal crystal structure.

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4. Hence, the layers of metal atoms are prevented from sliding over each

other easily. This makes the alloy harder and stronger, less ductile and less

malleable than its pure metals.

5. The properties of a pure metal are thus improved by making them into

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

a) To increase the hardness and strength of a metal

b) To prevent corrosion or rusting

c) To improve the appearance of the metal surface

9.4 SYNTHETIC POLYMERS

9.4.1 The meaning of polymers

1. Polymers can be defined as large molecules composed of numerous

smaller, repeating units known as monomers which are joined by covalent

bonds.

2. Polymerisation is the chemical process by which the monomers are joined

together to form the big molecule known as the polymers.

3. There are two types of polymerization process:

a) Addition polymerization

b) Condensation polymerization

4. A polymer is a very big molecule (macromolecule). Hence, the relative

molecular mass of a polymer is large.

5. The properties of polymer are different from its monomers.

6. Polymers can be divided into two types:

a) Naturally occurring polymers

i. This type of polymer exists in living things in nature like the plants

and animals.

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ii. Examples of naturally occuring polymers are:

a) Protein

b) Carbohydrate

c) Natural rubber

iii. Naturally occuring polymers are formed by the joining of

monomers by polymerization.

Protein is formed by the joining of monomers known as amino acid.

Carbohydrate is formed by the joining of monomers known as glucose.

Natural rubber is formed by the joining of monomers known as isoprene.

b) Synthetic polymers

1. This type of polymer are man-made by chemical process in

the laboratories.

The raw material for synthetic polymers are obtained frompetroleum.

The types of synthetic polymers include:

a) Plastics

b) Fibres

c) Elastomers

4. Examples of plastics are

polythene(polyethylene),polyvinylchloride(PVC), polypropene

(polypropylene), polystyrene , Perspex and bakelite.

5. Polythene and PVC are produced by addition

polymerization

6. Examples of synthetics fibres are nylon and terylene. They

are produced by condensation polymerization.

9.4.2 Advantages of synthetic polymers

Strong and light

Cheap

Able to resist corrosion

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Inert to chemical reactions

Easily moulded or shaped and be coloured

Can be made to have special properties

9.4.3 Environmental pollution caused by synthetic polymers

a) As most of polymers are non-biodegradable, they will not

decay like other organic garbage.

b) Burning of polymers release harmful and poisonous gases.

9.4.4 Methods to overcome the environmental pollution caused by synthetic

polymers

a) Reduce, reuse and recycle synthetic polymers

b) Develop biodegradable polymers

9.5 GLASS AND CERAMICS

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

2. Both glass and ceramic have the same properties as follow

a) Hard and brittle

b) Inert to chemical reactions

c) Insulators or poor conductors of heat and electricity

d) Withstand compression but not stretching

e) Can be easily cleaned

f) Low cost of production

3. Differences between glass and cerement are, glass is transparent, while

ceramic is opaque. Ceramic can withstand a higher temperature than normal glass.

4. Types of glass are

a) Fused glass

It is consist mainly of silica or silicon dioxide

It has high heat resistance

b) Soda lime glass

It cannot withstand high temperatures

c) Borosilicate glass

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It can withstand high temperature

d) Lead glass

High refractive index

5. Uses of improved glass for specific purpose

a) Photochromic glass

It is sensitive to light intensity

b) Conducting glass

It conducts electricity

6. Ceramic is a manufactured substances made from clay, with the

main constituent of aluminosilicate with small quantity of sand and feldspar.

7. Superconductor is one improved ceramics for specific purposes.

Glass

1. Glass is made up from sand.

2. The major component of glass is SiO2.

3. There are four types of glass which are as follows:

Fused glass

Soda-lime glass

Borosilicate glass

Lead crystal glass

Name of glass PropertiesChemical

compositionExamples of uses

Fused glassVery high softening

point (1700 C)

hence, highly heat

resistant

Transparent to

ultraviolet and

infrared light

SiO2 (99%)

Ba2 O 3 (1%)

Telescope mirrors,

Lenses

Optical fibres

Laboratory glass

wares

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Difficult to be made

into different shapes

Does not crack when

temperature changes

(very low thermal

expansion coefficient)

Very resistant to

chemical reactions

Soda lime glass

Low softening point

(700 C), hence, does

not withstand heating

Breaks easily

Cracks easily with

sudden temperature

changes (high

coefficient of

expansion)

Less resistant to

chemical reactions

Easy to be made into

different shapes

SiO2 (70%)

Na2O (15%)

CaO (3%)

Others (5%)

Bottles

Windowpanes

Light bulbs

Mirrors

Bowls

( The most widely

used type of glass)

Borosilicate

glassHigh softening point

(800C). Thus it is

heat resistant

Does not crack easily

with sudden

temperature changes

Transparent to

SiO2 (80%)

Ba2 O 3 (15%)

Na2O (3%)

Al 2 O 3

Laboratory apparatus

Cooking utensils

Electrical tubes

Glass pipelines

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ultraviolet light

More resistant to

chemical reactions

Does not break easily

Lead crystal

glass

Low softening point

(600 C)

High density

High refractive index

Reflects light raysand appears spar

kling

SiO2 (55%)

PbO( 30%)

K2O (10%)

Na2O ( 3%)

Al2 O 3 ( 2%)

Decorative items

Crystal glass-

wares

Lens

PrismsChandeliers

Ceramics

1. Ceramic is a manufactured substance made from clay that is dried and then

baked in a kiln at high temperature.

2. The main constituent of clay is aluminosilicate, (which consist of aluminium

oxide and silicon dioxide) with small quantities of sand and feldspar.

3. Kaolinite is an example of high

4. Red clay contains iron (III) oxide which gives the red colour .

5. General uses ceramics are as follows of :

very hard and strong but brittle

inert to chemical reaction

has a very high melting point

good electric and heat insulator

able to withstand compression

9.6 COMPOSITE MATERIAL

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1. A composite material is a structural material formed by

combining two or more materials with different physical properties, producing a

complex mixture.

2. The composite material produced will have different properties

far more superior to the original materials.

3. The composite material produced are harder, stronger, lighter,

more resistant to heat and corrosion and also for specific purposes.

4. When composite material is formed, the weakness of the

components will not exist anymore.

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Composite material Component Properties of

component

Properties of composite

Reinforced concrete

Concrete Hard but brittle,

With low tensile

strength

Stronger, higher tensile

strength, not so brittle,

does not corrode easily,

can withstand higher

applied forces and loads,

relatively cheaper

Steel Hard with high tensile

strength but expensive

and can corrode

Fibre optics

Glass of low

refractive index

Transparent, does not

reflect light rays.

Reflect light rays and

allow light rays to travel

along the fibreGlass of high

refractive index

Heavy, strong but

brittle and non-

flexible

Fibreglass

Glass Heavy, strong but

brittle and non-

flexible

Light, strong, tough,

resilient and flexible,

with high tensile strength

and not flammablePolyester plastic Light, flexible, elastic

but weak and

inflammable

Photochromic glass

Glass Transparent and notsensitive to light

Sensitive to light:darkness when light

intensity is high,

becomes clear when

light intensity is low

Silver chloride, or

silver bromide

Sensitive to light

Figure 9.9 Composite material and their new properties

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22047806 Chemistry Form 4 Chapter 9

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