Chemistry Form 4 Chapter 9

[MANUFACTURED SUBSTANCES IN INDUSTRY] September 20, 2010

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MANUFACTURED SUBSTANCES IN

INDUSTRY

Sulphuric acid

Ammonia

Synthetic polymers

Glass and Ceramics

Alloys

Composite Materials

CONCEPT MAP

MANUFACTURED SUBSTANCES

IN INDUSTRY

OBJECTIVE :

1. Understanding the manufactured of sulphuric acid.

2. Synthesis the manufacture of ammonia and its salts.

3. Understands alloys.

4. Evaluate the uses of synthetic polymers.

5. Apply the uses of glass and ceramics.

6. Evaluate the uses of composite materials.


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Sulphuric Acid

Uses of Sulphuric Acid

Sulphuric acid is very important industrially, and has many uses including:

a. The production of fertilisers such as ammonium sulphate, potassium sulphate, calcium

superphosphate (Ca(H<2PO4)2), etc.; these are straight fertilisers, as they supply one of

the important elements of nitrogen, phosphorus, or potassium (NPK);

b. The manufacture of non-soapy detergents: modern detergents are organic compounds

'sulphonated' with concentrated sulphuric acid;

c. The making of artificial silks like rayon: here, the fine threads in the alkaline cellulose

solution are neutralised by passing them through a bath of sulphuric acid;

d. The cleaning of metals by removing the surface oxide coating: this is called pickling and

is important in preparing articles for electroplating.

e. Its use as an electrolyte inside batteries for cars: most car batteries are made up of lead

plates in a sulphuric acid electrolyte; occasionally, the electrolyte needs to be 'topped

up' with distilled water ; this is because small amounts of hydrogen and oxygen gases

are given off by the chemical changes inside the battery, and therefore the sulphuric

acid loses water and becomes too concentrated ; in the manufacture of drugs, paints,

dyes and many other chemicals .

Manufacture of Sulphuric Acid: The Contact Process

The large-scale manufacture of this acid is extremely important as it is the most

common acid used in industry, with over 1 000 million metric tonnes being produced

annually.

It is manufactured by the Contact Process.

Stage 1

Combustion of Sulphur sulphur + oxygen sulphur dioxide

S (s) + O2 (g) ---> SO2 (g) or

Heating of metal sulphide such as lead(II) sulphide

2PbS(s) + 3O2(g) ---> 2PbO(s) + 2SO2(g)

or Combustion of hiydrogen sulphide

2H2S(g) + 3O2(g) ---> 2SO2(g) + 2H2O(ce)


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The raw materials are sulphur and air (oxygen). Sulphur dioxide is produced by burning either

sulphur or ores which contain sulphur.

Purification of sulphur dioxide

1. The sulphur dioxide is then purified, by removing impurities like arsenic compounds which

would otherwise poison the catalyst.

2. It is then passed through an electrostatic dust precipitator, which, as its name implies,

charges dust particles which are then removed by being attracted to oppositely charged

plates.

Stage 2

Formation of Sulphur trioxide sulphur dioxide + oxygen ---> sulphur trioxide 2SO2 (g) + O2 (g) ---> 2SO3 (g)

Catalyst: vanadium(V) oxide

Temperature: 450°C

Pressure: 2-3 atmospheres

Sulphur dioxide and air are then washed, dried and passed over a vanadium(V) oxide catalyst at

450°C and 2-3 atmospheres.

The reaction is reversible but at these temperatures and pressures, 98% conversion to sulphur

trioxide is achieved:

This reaction is exothermic, which means it favours a low temperature for high conversion to

sulphur trioxide.

Stage 3

Formation of oleum H2S2O7

sulphur trioxide + concentrated sulphuric acid ¾¾®oleum

SO3(g) + H2SO4(aq) ---> H2S2O7(l)

The next step is to dissolve the sulphur trioxide produced in concentrated sulphuric acid, to

form oleum, or fuming sulphuric acid.

Stage 4

Formation of Sulphuric acid Oleum + water ---> sulphuric acid

H2S207 (1) + H2O (1) ---> 2H2SO4(aq)

This oleum is then diluted with water to the required strength of acid:


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Although this may seem a roundabout route to take to form the acid, it is necessary because

sulphur trioxide cannot be dissolved directly in water as it reacts too violently, forming tiny droplets of

sulphuric acid which are very difficult to remove.

Sulphur Dioxide as pollutant

2. Sulphur dioxide (SO2) is the pollutant primarily associated with acid rain.

3. Gaseous at normal temperature and pressure it dissolves in water and readily oxidises to

sulphuric acid.

4. Levels of SO2 have reduced over recent years with a move away from widespread burning of

coal in homes and factories.

5. It is one of the main pollutants that led to the introduction of legislation governing atmospheric

pollution such as the 1956 Clean Air Act.

6. Sources of Sulphur Dioxide

7. The principal source of SO2 is from the combustion of fossil fuels in domestic premises and ,

more importantly, non-nuclear power stations.

8. Fossil fuel burning power stations account for around two thirds of total SO2 emissions in the

UK.

9. Other industrial processes contribute a further 20%, with vehicles, primarily diesel, accounting

for a mere 2%.

10. Health effects :

SO2 is an irritant when it is inhaled and at high concentrations (over 1000ppb) may

cause severe problems in asthmatics such as narrowing of the airways, known as

bronchoconstriction.

Sulphuric acid

to make fertilisers, polymers,

detergents, pigments

manufactured by the contact process

T : 450°C-550°C

P : 1 atmCatalyst : V2O5


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Ammonia and its Salts

1. Uses of ammonia

a. Manufacture of Fertilizers I. The main use of ammonia is in the manufacture of fertilizers.

II. Approximately 75% of all ammonia produced is converted into various ammonium compounds

like ammonium sulphate (NH4)2SO4, ammonium nitrate NH4NO3, ammonium phosphate

(NH4)3PO4 and urea NH2CONH2.

III. These compounds are called nitrogenous fertilizers.

Example ;

Ammonium sulphate (NH4)2SO4

H2SO4(aq) + 2NH3(aq) --->(NH4)2SO4(aq)

Ammonium nitrate NH4NO3

HNO3(aq) + NH3(aq) ---> NH4NO3(aq)

Ammonium phosphate (NH4)3PO4

H3PO4(aq) + 3NH3(aq) ---> (NH4)3PO4(aq)

Urea NH2CONH2

CO2(g) + NH3(g) ---> CO(NH2)2(p) + H2O(l)

IV. They are solids for ease in handling and water soluble so that they seep into the soil to be

absorbed by the roots of the plant. V. Nitrogen is an essential element for healthy plant growth as we saw earlier with the nitrogen

cycle. Nitrogen is essential for making proteins which are needed for healthy growth of stems

and leaves. The proportion of nitrogen present in a particular fertilizer can be calculated and is

usually quoted as an 'N' value on the fertilizer bag.

b. Solvent Uses 1. Aqueous ammonia is used as a degreasing agent, as it is a good solvent of grease and

fat.

2. Many household cleaners boast of the 'power of ammonia' for removing grease stains

around the kitchen.

3. However, it is wrong, as stated in some commercials, to talk of 'liquid ammonia'.

4. It is more accurate to say 'ammonia solution', as ammonia does not liquefy until a

temperature of -34 °C is reached.


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Characteristic of ammonia

React with acid to form salt and water

1. 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 solution react with positive ions

2. Ammonia dissolve into water to form ammonium and hydroxide ion.

NH3 + H2O ---> NH4+ + OH-

3. The hydroxide ion can react with many kinds of positive ion to form precipitate.

Example

Mg2+ + 2OH- ---> Mg(OH)2

Fe2+ + 2OH- ---> Fe(OH)2

Al3+ + 3OH- ---> Al(OH)3

Testing for Ammonia Gas

1. Ammonia is the only common alkaline gas, so it can be identified with moist red litmus paper

turning blue.

2. However, a more specific chemical test is to hold close to the suspected ammonia, a glass rod

dipped into some concentrated hydrochloric acid.

3. This will give off fumes of hydrogen chloride gas which, in the presence of ammonia, form a

dense, white 'smoke' of ammonium chloride:

4. ammonia gas + hydrogen chloride gas ---> ammonium chloride

NH3 (g) + HC1 (g) ---> NH4C1 (s)

5. In the same way, mixing a gas jar of hydrogen chloride and ammonia gas produces the same

dense, white smoke. The smoke again is the fine-particled solid called ammonium chloride.

The Haber Process

1. The reaction Ammonia is made by the Haber process from nitrogen and hydrogen:

N2(g) + 3H2(g) ---> 2NH3(g); Heat of reaction = -92 kJ mo1-1

The reaction is exothermic, and involves a decrease in the number of moles of gas.


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2. Sources of the raw material

Hydrogen

Hydrogen is produced industrially from cracking oil

Nitrogen

Nitrogen from liquefaction of the air

3. Condition

Catalyst Iron

Promoter Aluminium oxide

Ratio of Hydrogen and Oxygen

The two gases are combined directly in a ratio of 3 : 1

Temperature At 450 °C An application of Le Chatelier's shows that the forward reaction should be assisted by a low temperature. At low temperature, the rate of attainment of equilibrium is low. At high temperature, the position of equilibrium is over to the left. A compromise temperature is adopted, and a catalyst is employed to speed up the attainment of equilibrium concentrations.

Pressure At 200-1000 atm An application of Le Chatelier's shows that the forward reaction should be assisted by a high pressure.

4. Products The yield is about 10%, and unreacted gases are recycled

When the ammonia has been produced, it is liquefied 'out', by reducing the temperature to -

34°C(239 K)

to make fertilisers, nitric acid, and as a cooling agent

(refrigerant)

manufactured by the Harber process

T : 450°C-550°C

P: 200-500 atmCatalyst : Iron

Ammonia and its Salts


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Alloys

1. An alloy is a mixture of two or more metals mixed in a certain percentage.

Characteristic of metal

A pure metal has the following characteristics:

1. Ductile – can be drawn into wires

2. Malleable – can be made into sheets

3. High melting and boiling points

4. High density

5. High electrical conductivity

I. Many metal are also soft. Metals like iron and copper also form oxides easily.

II. As a result, the uses of pure metals are limited, and alloys are made to improve the malleability,

ductileness and hardness of a metal.

III. A pure metal is composed of layers of atoms which are arranged in an even, orderly and close

manner at fixed positions (see Figure 9.8). Each atom is surrounded by 8-12 atoms.

IV. This arrangement of atoms causes the metal to be very dense with high melting and boiling

points. The strong forces of attraction between atoms require a great amount of heat to

overcome.

V. However, in spite of strong forces of attraction between atoms, the metal is not hard. If a force

is applied on the metal, the layers of atoms can glide and slide on top of each other, causing

them to move to new positions. This allows the metal to be drawn into wires (ductile). (See

Figure 9.9.)

VI. The spaces left naturally between layers of metal atoms also make it easy to be beaten into

sheets (malleable).

VII. The formation of alloys occurs when these empty spaces between metal atoms are filled with

atoms of another metal, which may be higher or smaller than the original metal atoms. (Figure

9.10)

VIII. The foreign atoms are usually another metal but sometimes a non-metal, like a carbon or silicon

is used.


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Purpose of Making Alloys

Alloys are made to

1. Increase the hardness of metals.

2. Prevent the corrosion of metals.

3. Improve the beauty and luster of metals.

Composition, Characteristic, and Uses of Alloy

Alloy Composition Properties Uses

Cupronickel (Coins)

Cu 75% Ni 25%

Hard, strong, resists corrosion

Coins

Duralumin Al 95% Cu 4% Mg 1%

Light, strong Aeroplane parts, electric cables, racing bicycles

Steel Fe 99% C 1%

Hard, strong, cheap Vehicles, ships, bridges, buildings

Stainless steel Fe73% Cr 18% Ni 8% C 1%

Hard, rust resistant Kitchen appliances, watches, machine parts, knives, forks, spoons

Bronze Cu 90% Sn 10%

Hard, strong, shining Decorative items, medals, artwork, pots and pans

Brass Cu 70% Zn 30%

Harder and cheaper than Cu

Decorative items, electrical appliances, musical instruments, bell, nails, screw, pots

Snider Pb 50% Sn 50%

Low melting point, strong Welding and soldering work

Pewter Sn 91% Sb 7% Cu 2%

Malleable, ductile, rust resistant

Decorative items, souvenirs

Magnalium Al 70% Mg 30%

Light, strong Tyre rim of racing cars, skeletal body of aeroplanes


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Synthetic Polymers

1. Synthetic polymer is a polymer that is manufactured in industry from chemical substances

through the polymerisation process. Through research, scientists are now able to copy the

structure of natural polymers to produce synthetic polymers.

2. Plastics, synthetic fibres and elastomers are examples of synthetic polymers.

3. The raw materials for the manufacture of synthetic polymers are distillates of petroleum.

4. The two types of polymerisation are:

5. Polymerisation by addition

6. Polymerisation by condensation

7. 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. Examples of

polymers produced through this process are polythene, PVC perspex and other plastics.

8. 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.

Alloys

to increase hardness and

strength

to prevent corrosion

to improve the

appearance

steel, bronze, brass,

magnalium, pewter


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Issue in using synthetic polymer

1. Synthetic polymers have multiple uses in daily life because of the following properties:

2. Light and strong

3. Cheap

4. Withstand corrosion and chemical reaction

5. Withstand action of water

6. Synthetic polymers are also used to replace natural polymers such as cotton, silk and rubber.

7. However, synthetic polymers cause environmental pollution.

8. Most polymers are not biodegradable . Polymers cannot be decomposed biologically or

naturally by bacteria or fungi as in the case of other garbage. Thus, the disposal of polymers has

resulted in environmental pollution because they remain in the environment forever.

9. Plastic containers and bottles strewn around become good breeding places for mosquitoes

which cause dengue fever, or malaria.

10. 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.

polythene : to make plastic bags,container and toys

polypropene : to make plastic bottles, tables, and chairs

PVC : to make water pipes, rain clothes, and wire casing


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Glass and Ceramics

Properties of glass and ceramic:

1. Both have the following properties:

2. Hard and brittle

3. Do not conduct heat electricity

4. Inactive towards chemical reactions

5. Weak when pressure is applied

6. Can be cleaned easily

Glass

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

dioxide.

2. Glass has the following properties:

3. Transparent and not porous

4. Inactive chemically

5. Can be cleaned easily

6. Good insulators of heat and electricity

7. Hard but brittle

8. Can withstand compression but not pressure

9. Due to the above reasons and the low cost involved to produce glass, it is used in industry to

make bottles, cooking utensils, plates and bowls, laboratory apparatus (such as conical flask,

beakers and test tubes), window panes, bulbs and others.

10. Different types of glass can be obtained depending on the composition of substances in it.

Summary

Glass Composition Properties Uses

Soda lime,glass SiO2 – 70% Na20 – 15% CaO – 10% Others – 4%

• Low melting point (700°C) • Mouldable into shapes • Cheap • Breakable • Can withstand high heat

Glass containers, Glass panes, Mirrors, Lamps and bulbs, Plates and bowls Bottles

Lead glass (crystal)

SiO2 – 70% Na20 – 20% PbO – 10%

• High density and refractive index • Glittering surface • Soft • Low melting point (600°C)

Containers for drinks and fruit Decorative glass and lamps Crystal glassware Lenses for spectacles


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Borosilicate glass (Pyrex)

SiO2 – 80% B203 – 13% Na2O – 4% Al203 – 2%

• Resistant to high heat and chemical reaction • Does not break easily • Allows infra-red rays but not ultra-violet rays

Glass apparatus in laboratories Cooking utensils

Fused silicate glass

SiO2 – 99% 6203 - 1%

• High melting

Composite Materials

1. Composite materials are substances which contain 2 or more materials that combine to produce

new substances with different physical properties from the original substances.

2. They are used to make various substances in daily life because of the following reasons:

3. Metals corrode and are ductile and malleable

4. Glass and ceramics break easily

5. Metals are good conductors but have high resistance, leading to loss of electrical energy as heat

6. Plastics and glass can withstand heat to certain level only.

7. Composite materials have been created to overcome these problems and to make materials

stronger, more long-lasting and light for specific purposes.

Construction materials,

household items, laboratory apparatus

Glass and Ceramics

Fused glass, soda glass, borosilicate glass, lead glass


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Some composite materials and their components are:

Uses of Composite Materials :

1. Reinforced concrete

2. Optical fibre

3. Photochromic glass

4. Plastic reinforced with glass

5. Superconductor

reinforced concrete

superconductors

fibre opticfibre glass

photocromic glass


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Conclusion

1. Chemical processes change raw materials into materials with certain properties that can we use

2. As technology evolves, new uses for existing materials would be found in many areas such as

household use aerospace modern architecture, microelectronics, telecommunication and

scientific research.

3. In many cases synthetic polymers, alloys and composites can be manufactured to meet our

needs.

4. However, they can never totally replace the traditional materials that we have been using for

many generations like wood and steel.

5. The synthetic materials, if not managed properly, will harm the environment.

References

1. http://wiki.one-

school.net/index.php/Synthesising_the_manufacture_of_ammonia_and_its_salts

2. Tan Yin Toon, Loh Wai Leng, Tan On Tin, Success Chemistry SPM, Oxford Fajar sdn Bhd.

3. Form 4 Chemistry Text Book.

4. Jamalia Jamil, Au Wei Leong, Smart Chemistry Form 4,Preston Corporation Sdn Bhd.

http://wiki.one-school.net/index.php/Synthesising_the_manufacture_of_ammonia_and_its_salts

http://wiki.one-school.net/index.php/Synthesising_the_manufacture_of_ammonia_and_its_salts

Chemistry Form 4 Chapter 9

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