Chemistry Form 4 Chapter 9

August 4, 2017 | Author: dinda syi | Category: Sulfuric Acid, Sulfur, Glasses, Polymers, Metals
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CONTENT Content Introduction 9.1 Sulphuric acid 9.1.1 Properties of sulphuric acid 9.1.2 The uses of sulphuric acid 9.1.3 The industrial process in manufacture of sulphuric acid 9.1.4 Environmental pollution by sulphuric acid 9.2 Ammonia and its salt 9.2.1 Properties of ammonia 9.2.2 The uses of ammonia 9.2.3 The industrial process in manufacture of ammonia 9.3 Alloys 9.3.1 Physical properties of pure metals 9.3.2 Meaning and purpose of making alloys 9.4 Synthetic polymers 9.4.1 The meaning and types of polymers 9.4.2 Advantages of synthetic polymers 9.4.3 Environmental pollution caused by synthetic polymers 9.4.4 Methods to overcome the environmental pollution caused by synthetic polymers 9.5 Glass and ceramics 9.6 Composite material Conclusion References

Page 3 4 5 7 10 11 12 13 14 15 16 17 17 18 18 22 24 25

INTRODUCTION All the objects that exist around us are made up of chemical substances. These objects exist an element, compound or mixture. All these objects contribute benefit to humankind. As time goes on, human has done many researches to ensure all these chemical substances will be enough for the use of themselves.


Chapter 9 of Form 4 syllabus introduces the students with manufactured substances in industry. This is important for the students to appreciate the knowledge of chemistry that is still new for themselves. Personally, I think that this chapter is an interesting chapter as it revealed the way of scientist produces the material around me. It also gives me new knowledge of the uses of chemical substances that I usually found in the laboratories. I hope, by learning this chapter, I will be more interested in learning chemistry as it will help me in the future. All the equations from this chapter make me more understand of the previous chapters.

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.

Figure 9.1 A molecule of sulphuric acid.


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.

Soluble in water Non-volatile acid

Diprotic acid

Properties of sulphuric acid

Highly corrosive

Oily liquid


Viscous colourless liquid

Figure 9.2 Properties of sulphuric acid

9.1.2 The uses of sulphuric acid 1) To manufacture fertilizers There are many fertilizers that can be made of sulphuric acid. Some of them are: a)

Calcium dihydrogen phosphate (superphosphate) 2 H2SO4 + Ca3(PO4) 2 → Ca(H2 PO4) 2 + 2CaSO4 sulphuric acid + tricalcium phosphate → calcium dihydrogen phosphate 4


Ammonium sulphate +2NH3 → (NH4) 2 SO4 H2SO4 sulphuric acid + aqueous ammonia → ammonium sulphate


Potassium sulphate +2NH3 → (NH4) 2 SO4 H2SO4 sulphuric acid + aqueous ammonia → ammonium 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 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 oxidizing agent d. As a sulphonating agent e. As a catalyst

Remove metal oxides from metal surfaces before electroplating

As an electrolyte in lead-acid accumulators

Manufacture pesticides

Uses of sulphuric acid Manufacture paint pigments

Manufacture fertilizers

Manufacture detergents

Manufacture synthetic fibres

Figure 9.3 Uses of sulphuric acid

Synthetic fibres 9% As an electrolyte 10%

Metal cleaning 2% Dyes 2% As an acid 2% Fertilisers 32%

Detergents 12% Paint pigment 15%

Other chemicals 16%


Figure 9.4 Uses of sulphuric acid in industry

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 water via the contact process. 3. The Contact process involves three stages. Sulphur acid

→ Sulphur dioxide → Sulphur trioxide → I




4. Stage I: Production of sulphur dioxide gas, SO2. This can be done by two methods, a)

Burning of sulphur in dry air. + O2 → S SO2


Burning of metal sulphide such as zinc sulphide in dry air. 2ZnS + 3O2 → 2SO2 + 2ZnO

5. Stage II: Conversion of sulphur dioxide to sulphur trioxide SO3. 7

This is then oxidised to sulfur trioxide under the following conditions: a) The presence of a vanadium(V) oxide as a catalyst. b) A temperature of between 450°C to 550°C. c) A pressure of one atmosphere 2 SO2 + O2 → 2 SO3 6. Stage III: Production of sulphuric acid a) Sulphur trioxide is dissolved in concentrated sulphuric acid, H2SO4 to produce oleum, H2S2O7

H2SO4+ SO3 →

b) Oleum is reacted with water to form concentrated H2SO4. H2S2O7+ H2O → 2 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


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


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

Sulphur or metal sulphide burned in air

Sulphur dioxide, SO2 8

a) the presence of a vanadium(V) oxide as a catalyst. b) a temperature of between 450°C to 550°C. c)

a pressure of one atmosphere

Sulphur trioxide, SO3 dissolved in sulphuric acid, H2SO4

Oleum, H2S2O7

diluted with equal volume of water H2O

Concentrated sulphuric acid H2SO4 Figure 9.5 Flowchart of Contact process

9.1.4 Environmental pollution by sulphuric acid 1.

Sulphur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned.


Sulphuric acid is formed by atmospheric oxidation of sulphur dioxide in the presence of water. It also produces sulphurous acid.


Sulphuric acid and sulphurous acid are constituents of acid rain.


Acid rain can cause many effects such as: i.

Corrodes concrete buildings and metal structure



Destroys trees and plants


Decrease the pH of th soil and make it become acidic


Acid rain flows into the rivers and increases the acidity of water and kill aquatic living things.


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


Remove sulphur dioxide from waste air by treating it with calcium carbonated before it is released.

9.2 AMMONIA AND ITS SALT 9.2.1 Properties of ammonia 1.

A colorless, pungent gas.


Its molecular formula is NH3 3.

It is extremely soluble in water.


It is a weak alkali.


It is about one half as dense as air

Figure 9.6 A molecule of ammonia.



It reacts with hydrogen chloride gas to produce

white fumes of ammonium chloride. NH3 + HCl → NH4Cl


Ammonia is alkaline in property and reacts with dilute acids in

neutralization to produce salts. For examples: NH3 + HNO 3 → NH4NO 3 2NH3 + H2SO4 → (NH4) 2 SO4

8. Aqueous solutions of ammonia produces OH − ions (except Na+ ion, K+ ion, and Ca 32+ ion) forming metal hydroxides precipitate. Fe + + 3OH− → Fe(OH) 3 Brownprecipitate

Mg2+ + 2OH− → Mg(OH) 2 Whiteprecipitate

9. Some metal hydroxides such as zinc hydroxide and copper (II) hydroxide dissolves in excess aqueous ammonia to form complexes. Zn(OH)2 + 4NH3→ [Zn(NH3)4] 2+ + 2OH −

Cu(OH)2 + 4NH3→ [Cu(NH3)4] 2+ + 2OH −

Extremely soluble in water

Weak alkali Properties of ammonia


Pungent smell


Figure 9.7 Properties of ammonia

9.2.2 The uses of ammonia 1.

The major use of ammonia and its compounds is as fertilizers.


Ammonia is also used for the synthesis of nitric acid.


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: Mass of nitrogen X 100%

Molar mass of fertilizers

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. 12

4. Hydrogen gas used in Haber process can be obtained by two methods: C + H2O → CO + a) The reaction between steam and heated coke (carbon) H2

b) The reaction between steam and natural gas ( consisting mainly of CH4 + 2H2O → CO2 + methane) 4H2

5. In the Haber process: 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 - 550°C. c) At this optimum temperature and pressure, ammonia gas is produced. N2+ 3H2 → 2NH3

9.3 ALLOYS 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. 13


Pure metals are soft because the orderly arrangement of atoms

enables 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. high density of

The close-packed arrangement of metal atoms results in the metals.

Good conductor of electricity High melting and boiling point High density

Properties of metals

Malleable Ductile

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. 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


To prevent corrosion or rusting


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 1.

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

and animals. 2. a)





Natural rubber 3.

Examples of naturally occuring polymers are:

Naturally occuring polymers are formed by the joining of

monomers by polymerization. 4.

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. 2.

The raw material for synthetic polymers are obtained frompetroleum.


The types of synthetic polymers include: a)








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 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


Develop biodegradable polymers


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


Both glass and ceramic have the same properties as follow a)

Hard and brittle


Inert to chemical reactions


Insulators or poor conductors of heat and electricity 17


Withstand compression but not stretching


Can be easily cleaned


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. a)

Types of glass are

Fused glass



is consist mainly of silica or silicon dioxide


has high heat resistance

Soda lime glass •It


cannot withstand high temperatures

Borosilicate glass •It


can withstand high temperature

Lead glass •


High refractive index 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 18

• Lead crystal glass

Name of glass


Chemical composition

Examples of uses

Very high softening point (1700 °C) hence, highly heat resistant Transparent to ultraviolet and infrared light Fused glass

SiO2 (99%) Ba2 O 3 (1%)

Telescope mirrors, Lenses

Difficult to be made

Optical fibres

into different shapes

Laboratory glass

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

SiO2 (70%) Na2O (15%) CaO


Others (5%)

Bottles Windowpanes Light bulbs Mirrors Bowls

sudden temperature

( The most widely

changes (high

used type of glass)

coefficient of expansion) Less resistant to chemical reactions Easy to be made into 19

different shapes

High softening point (800°C). Thus it is heat resistant Does not crack easily with sudden Borosilicate glass

temperature changes Transparent to

SiO2 (80%) Ba2 O 3 (15%)

Laboratory apparatus

Na2O (3%)

Cooking utensils

Al 2 O 3

Electrical tubes Glass pipelines

ultraviolet light More resistant to chemical reactions Does not break easily

Low softening point (600 °C) Lead crystal glass

High density High refractive index Reflects light rays and appears spar

SiO2 (55%) PbO( 30%) K2O (10%) Na2O ( 3%) Al2 O 3 ( 2%)

Decorative items Crystal glasswares Lens Prisms Chandeliers


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


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.

Composite material

Reinforced concrete


Properties of

Properties of composite


component Hard but brittle,

Stronger, higher tensile

With low tensile

strength, not so brittle,

strength Hard with high tensile

does not corrode easily,


strength but expensive and can corrode

Fibre optics

Glass of low

Transparent, does not

refractive index Glass of high

reflect light rays. Heavy, strong but

can withstand higher applied forces and loads, relatively cheaper Reflect light rays and allow light rays to travel along the fibre 21

refractive index

brittle and non-


flexible Heavy, strong but

Light, strong, tough,

brittle and non-

resilient and flexible,

flexible Light, flexible, elastic

with high tensile strength

Fibreglass Polyester plastic

and not flammable

but weak and

Photochromic glass


inflammable Transparent and not

Silver chloride, or

sensitive to light Sensitive to light

silver bromide

Sensitive to light: darkness when light intensity is high, becomes clear when light intensity is low

Figure 9.9 Composite material and their new properties


CONCLUSION We must appreciate these various synthetic industrial materials. One of the way is by doing continuous research and development ( R & D ) to produce better materials used to improve our standard of living. As we live in a changing world, our society is getting more complex. New materials are required to overcome new challenges and problems we face in our daily lives. Synthetic material are developed constantly due to the limitation and shortage of natural materials. New technological developments are used by scientists to make new discoveries. New materials for clothing, shelter, tools and communication to improve our daily life are developed continuously for the well-being of mankind. New needs and new problem will stimulate the development of new synthetic materials. For example, the new use of plastic composite material will replace metal in the making of a stronger and lighter car body. This will save fuel and improve speed. Plastic composite materials may one day used to make organs for organ transplant in human bodies. This will become necessity with the shortage of human organ donors. The understanding of the interaction between different chemicals is important for both the development of new synthetic materials and the disposal of such synthetic materials as waste. A responsible and systemic method of handling the waste of synthetic materials and their by-product is important to prevent environmental pollution. The


recycling and development of environmental friendly synthetic material should be enforced.


Tan Yin Toon, Loh Wai Leng, Tan On Tin, 2008, SUCCESS

Chemistry SPM, Oxford Fajar Sdn.Bhd. 2.



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