Chemistry Chapter 9 Form 4 manufactured substances in industry

7/29/2019 Chemistry Chapter 9 Form 4 manufactured substances in industry

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9.1..SULPHURIC ACID

9.1.1 Uses of sulphuric acid

1. Sulphuric acid is one of the most important industrial chemicals. About 140 milliontonnes are manufactured in the world every year.

2. It is used in most industries ranging from agriculture fertilisers to paints, soap andthe cleaning of rust.

3. The main use of sulphuric acid is in producing fertilisers, particularlysuperphosphate and ammonium sulphate.

a) Superphosphate fertiliser :It is manufactured from the reaction between sulphuric acid and calcium

phosphate.

2H SO (1) + CA(PO)(s) Ca(HPO)(1) + 2CaSO(s)

b) Ammonia sulphute fertiliser :It si manufactured by the reaction between sulphuric acid and ammonia.

2NH(aq) + HSO(aq) (NH)SO(aq)

c) Potassium sulphate :It is manufactured by the neutralisation of sulphuric acid and potassium

hydroxide.

2KOH(aq) + HSO(aq) KSO(aq) + 2HO(1)

4. Initially, sulphonic acid is produced by the reaction between sulphuric acid andhydrocarbon compound.

making fertilisers

paints

chemicals

detergents

removing rust from steel

other uses

Uses of sulphuric acid, H SO

A molecule of sulphuric acid


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5. Sulphonic acid then reacts with sodium hydroxide to form sodium alkyl sulphonate,which is a detergent.

6. Accumulators need an electrolyte to carry charges and to react with the positive andnegative plates during the charging and discharging processes.

7. In the acid accumulator, sulphuric acid acts as the electrolyte.Table 9.1 Uses of sulphuric acid in the laboratory

Uses of

Sulphuric acid

Example

Drying agent Concentrated sulphuric acid is generally used to dry gas in the

laboratory. However it is not suitable to dry alkaline gases such

as ammonia.

Oxidising agent Concentrated sulphuric oxidises copper to form copper( )

sulphate.2HSO(1) + Cu(s) CuSO(aq) + 2HO(1) + SO (g)

However dilute sulphuric acid does not react with copper.

Dehydrating agent When concentrated sulphuric acid is added to sugar, a violent

reaction accurs.

The water content in the sugar is extracted by the acid and the

sugar becomes carbon.

Strong acid It reacts with the salt of the weak acid such as sodium

ethanoate to form a weak acid.

2CHCOONa(s) + HSO(1) 2CHCOOH(aq) + NaSO(aq)

9.1.2 Manufacture of Sulphuric Acid1. Today, sulphuric acid is made from sulphur dioxide, by the Contact Process.

There are three stages for the production of sulphuric acid by the Contact

Process.


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Stage 1

a. In the furnace, sulphur is burnt in dry air to produce sulphur dioxide.S(1) + O(g) SO(g)

b. In the Contact Process, sulphur powder is sprayed inside a furnace at a temperatureof 100C. Here sulphur is converted to sulphur dioxide.

c. Sulphur dioxide can also be produced by heating metal sulphides such as zinesulphide.

Stage 2 (Preparation of sulphur trioxide)

a. Sulphur dioxide and air are passed over a catalyst called vanadium(V) oxide, (VO).b. he temperature used here is aout (450 500)C. If the temperature is less than

this range, the vanadium(V) oxide may not be able to catalyse.

c. The reacting pressure is about 2 to 3 atmospheres.d. At this stage, sulphur trioxide is produced.

2SO(g) + O(g) 2SO(g)

e. This reaction will produce about 98% sulphur trioxide.Stage 3 (Formation of sulphuric acid)

a. The sulphur trioxide is dissolved in concentrated sulphuric acid to form a productcalled oleum, HSO. his is carried out until the concentrated sulphuric acid has

reached a concentration of 99.5%.

SO(g) + HSO(1)

b. The product, oleum will not show any property of an acid. This is because, oleum willnot ionise without the presence of water.

c. Water is then added to the oleum to produce concentrated sulphuric acid.HSO(1) + HO(1) 2HSO(1)

d. The reaction of (a) and (b) is equivalent to dissolving sulphur trioxide in water.


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SO(g) + HO(1) HSO(aq)

e. However this reaction is not carried out in industry. This is because the reaction istoo vigorous.

f. It produces a large cloud of sulphuric acid mist. This mist is corrosive and pollutes theair.

Contact Process

Burnt in air

Further oxidation

Catalyst: VO

emperature: (450 500) C

Pressure: 1 atm

Dissolves in concentrated sulphuric acid, HSO

Dilute with water

Sul hur

Sulphur dioxide SO

Concentrated sulphuric acid, HSO

Sulphur trioxide SO

Oleum HSO


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9.1.3 Sulphur Dioxide and Environmental Pollution1. Sulphur dioxide is the main by product produced when sulphur-containing fuels

such as coal or oil are burned.

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

3. Sulphuric acid and sulphurous acid are constituents of acid rain.4. Acid rain can cause many effects such as:

I. Corrodes concrete buildings and metal structure.II. 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 calciumcarbonated before it is released.


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Acid rain and environmental pollution

9.2..AMMONIA AND ITS

SALTS

9.2.1 USES OF AMMONIA

1. Ammonia that is produce commercially has many uses.2. It uses:

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

II. To manufacture nitric acid and explosive.III. In the making of synthetic fibre and nylon.IV. As a degreasing agent in aqueous form to remove greasy stains in the

kitchen.

9.2.2 PROPERTIES OF AMMONIA GAS1. The physical properties of ammonia gas include the following:

I. It colourless and has a pungent gas.II. It is highly soluble in water and form a weak alkaline solution.

NH(g) + HO(1) NHOH(aq)

III. It less dense than air.IV. It easily liquefied (at about 35.5C) when cool.V. Ammonia melts at -77.7C and oils at -33.35C.

VI. Its density is 0.68 (at its boiling point and at 1 atmosphere ofpressure)

2. The chemical properties of ammonia gas:I. Ammonia dissolves into water to give an alkaline solution with a pH

value of 9-10.

II. Its turns moist red litmus paper to blue.III. Ammonia is an alkali. It will neutralise acids to make ammonium salts.

NH(g) + HSO(aq) (NH)SO(aq)

Ammonia sulphuric acid ammonium sulphate

NH(g) + HNO(aq) NHNO(aq)

Ammonia + nitric acid ammonium nitrate

A molecule of ammonia


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IV. Gaseous ammonia reacts with gaseous hydrogen chloride to formwhite fumes of ammonium chloride.

NH(g) + HCI(g) NHCI(s)

Ammonia + hydrogen ammonium chloride

chloride

V. When ammonia chloride heated, it changes back into ammonia andhydrogen chloride.

VI. Ammonia dissolves in water to form ammonium hydroxide.Ammonium hydroxide, NHOH, is strongly asic. It has similar

chemical properties as compared to other hydroxides of alkali metals.

VII. Ammonia reacts with metallic ions(except Na, Kand Ca)to formmetallic hydroxides.


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9.2.3 MANUFACTURE OF AMMONIA IN INDUSTRY(Haber Process)

1. Ammonia is made by synthesis through Haber Process.2. Nitrogen and hydrogen are combined directly together to form ammonia.3. To supply the Haber Process,

a) Nitrogen gas can be distilled from liquid air.b) Hydrogen is produced by electrolysing brine (sea water)

4. Nitrogen and hydrogen can also be obtained from natural gas (methane).5. The mixture of nitrogen and hydrogen gases is passed over an iron catalyst

under controlled optimum condition as below to form ammonia gas.

I. Temperature: 450-500CII. Pressure: 200-500 atmospheres

III. Catalyst used: Iron fillings6. Under these control optimum condition, only 15% of the gas mixture turn

into ammonia gas. The nitrogen and hydrogen that have not reacted are thenflow back over the catalyst again in the reactor chamber.

7. The ammonia product is then cooled at a low temperature so that itcondenses into a liquid in the cooling chamber.


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The manufacture of ammonia, NH3 through the Haber Process

1) Gases mixed and scrubbedHaber process comines N gas from the air with H gas from natural gas to

form NH. The two gases are mixed. The mixture is scrubbed to get rid of

impurities.

2) CompressorOne volume of N gas and three volume of H gas is compressed to a

pressure of 200 500atm

N(g) + 3H(g) 2NH(g)

3) ConverterThen, it goes to the converter. It is then passed through layers of iron

catalyst with aluminium oxide as a promoter at a temperature of 450C

500C

4) CoolerA mixture of three gases leaves the converter. It is cooled until the ammonia

condenses. The nitrogen and hydrogen are pumped back to the converter

for another chance to react.

5) storage tanksNH is formed and then liquefy and separated to get a better yield. he NH

is run into tanks and stored as a liquid under pressure.


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Making Ammonia in School Laboratory

1. Ammonia can be produced in the laboratory by warming an ammonium saltwith an alkali.

2. Example: heating ammonium chloride with sodium hydroxideNHCI(s) + NaOH(aq) NaCI(aq) + NH(g) + HO(I)

3. In the laboratory, a mixture of solid ammonium chloride and dry calcumhydroxide is heated.

4. The damp ammonia gas prepared in the laboratory can be dried by passing itthrough calcium oxide.

5.

Other drying agent agents such as concentrated sulphuric acid and anhydrouscalcium chloride cannot be used. They react with ammonia.

2NH + HSO (NH)SO

4NH + CaCI CaCI.4NH

FLOW CHART FOR THE HABER PROCESS

AMMONIUM FERTILIZERS

1. Nitrogen is required in large amount by plant to make proteins which arenecessary for growth and cell repair.

2. Most plant are not able to get a nitrogen supply directly from the airalthough it is abundant in the air (78%). Plants can only absorb soluble

nitrogen compounds from soil through their roots.

3. The nitrogen compounds are usually soluble nitric salt, ammonia andammonia salt which are manufacture as chemical fertilizer.

H N

450 - 500C

Refrigeration

NH


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4. Reactions of ammonia with acids produce ammonium fertilizers.

9.3..ALLOYS

9.3.1 Meaning of Alloy1. Alloys are materials that contain more than one element.2. Usually, alloys are mixtures of metallic elements two or more metals.3. Pure aluminium is light but not strong enough to make aeroplane bodies. If a

small amount of manganese and magnesium are added then an alloy

duralumin is formed this alloy is hard and strong for aeroplane frames.

4. Thus an alloy is a mixture of metals are made for a certain purpose.

9.3.2 Arrangement of Atoms in Metals

1. In pure metals, the atoms are all of the same size.2. They are arranged in layers as shown in the figure below.

3. When the pure metals are hit with a hammer, the layers of atoms can slideover each other easily.

4. Thus, pure metal can easily change its shape. They are said to be Ductile as they can be drawn into long wires Malleable as they can be hammered to form any shapes.


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9.3.3 Arrangement of Atoms in Alloys

1. Alloys have more than one kind of atoms. These different atoms are ofdifferent sizes. They are mixed when they are in the molten state (liquid).

2. The layers of atoms in an alloy cannot slide over each other as easily asshown in the figure below.

3. The movement of atoms get jammed up. This makes tem difficult to move.4. This makes the alloy not ductile and not malleable.5. However, alloys are harder and stronger than the original constituent metals.6. There are different ways of arranging the different atoms in alloys.

Solution alloys are homogeneous alloys in which the different atomsare distributed uniformly throughout.

In heterogeneous alloys, the different atoms are not distributeduniformly.

7. Homogeneous alloys have definite properties and compositions.


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9.3.4 Aim of Producing Alloys

1. The basic aim of making alloys is to modify the properties of the pure metalelements. Sometimes this is necessary to make ornaments.

2. Pure gold is too soft to be used in jewellery. However, an alloy of copper andgold is quite hard for this purpose.

3. To prevent or minimise corrosion Iron is easily corroded especially in polluted, acidic and damp

industrial areas.

An iron alloy will be less likely to rust if carbon, nickel, or chromium isadded to it.

Stainless steel is an alloy of iron. It will not rust even under extremeconditions.

The presence of chromium in it, will form chromium (III) oxide. The presence of nickel in it will form nickel (I ) oxide. The presence of layers of these oxides will prevent corrosion and

oxidation.

4. To improve the physical appearance Fresh metal surfaces are usually shinning. These shinning surfaces are usually tarnished if they are coated with

a layer of oxides.

Alloys are not easily oxidised. This is because the oxide layers are noteasily formed. Thus, surfaces of alloys will remain shinning for a

longer time.

Stainless steel utensils are more shinning then iron utensils.

9.3.5 Composition, properties and uses of alloys

1. Like metals, all alloys are conductors of Heat and Electricity

2. Like metals too, all alloys have shinning surfaces. They have a lustrousappearance. However, most alloys are more shinny than pure metals if they

are kept for a long time. This is because alloys do not corrode or oxidise

easily. Metals tend to have a layer of oxides after some time.


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3. Alloys are less malleable than metals. They are not easily hammered intosheets.


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9.4..SYNTHETIC POLYMERS

9.4.1 Meaning of Polymers1. Polymers are large molecules made up of many identical repeating sub-unitscalled monomers which are joined together by covalent bonds.

2. Monomers are joined into chains by a process of repeated linking known aspolymerisation.

3. A polymer may consists of thousands ofmonomers.4. The process of forming polymers ispolymerisation.5. If the molecules simply join together, then this type of polymerisation is

called additional polymerisation.

6. There are two main groups of polymers: Man-made polymers or synthetic polymers Natural polymers

9.4.2 Natural Polymers1. Rubber is an example of a natural polymer.2. Other natural polymers are :

a. Fat in cells;b. Carbohydrate in cells;c. Protein in cells.

3. All these substances are large molecules that are joined together. Thus, fats,carbohydrates and proteins are natural polymers.

9.4.3 Synthetic Polymers

1. Synthetic polymers are man-made polymers.2. The monomers used are usually obtained from petroleum after goingthrough the refining cracking processes.3. Examples: polythene, polyvinyl chloride (PVC) polystylene, Perspex , and

nylon.

4. Synthetic polymers are very stable and do not corrode or decay, and alsodifficult to dispose.

5. They may cause pollution, blockage of drainage systems and flash floods.


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Polythene

Open up of double bonds of ethene molecules

1. Double bonds of ethene molecules, open up to form single bonds.

Formation of polyethylene polymer

2. Opened molecules of ethene, join together to form polyethylene polymera. If ethene gas is heated under pressure, it will polymerise to form a

waxy white solid as shown in figure below.

b. This process is called man-made polymerisation.c.

Ethene is called a monomer and the product polythene is a syntheticpolymer.


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Perspex

PVC..

Polystyrene


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Synthetic polymers and their users

Synthetic Rubber

1. There are two main types of synthetic rubber :a. SBR rubber or styrene butadience.b. Neoptene.

2. SBR rubber or styrene- butadiencea. This rubber is made by combining one part of styrene (IUPAC name :

phenylethene) with three parts of butadience (IUPAC name : 1 , 3

diena).

Polymers Monomer Uses Characteristic

PVC Chloroethene, C H CI Drain pipes, insulation for

electric wiring, artificial

leather, water-proof

clothes, shoes

Tough and flexible

Polythene Ethylene, CH CH Plastic bags, cups and

wrappers

Not easily torn

Polypropene

(polypropylene)

Propene CH CHCH Film for packaging, snap-on

lids, bottles

Strong and light

Perspex Methyl 2-methyl

Propenoate

CH C(CH )COOCH

Lenses, window glass Light, strong and

stable to sunlight

Nylon

(polyamide)

Carboxylic acid Curtain rails, hinges, fibres

for clothes, ropes, stocking,

parachutes, fishing line

Strong and long

lasting, easy to wash.

Can be drawn into

threads

Terylene

(polyester)

Ethylene glycol and

terephthalic acid

Fibres for clothes, video

tape, plastic bottles

Keep in shape after

washing, light and

soft but strong

Polystyrene Styrene Foam drinking cups,

insulation, furniture,

packing materials

Strong and light. Can

be made into foam

Styrene and

butadience

undergo addition

reaction..


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b. This type of polymerisation is called copolymerisation.c. This polymer was developed during World War II and it used mainly to

make tyres.

3. Neoprenea. This rubber is made from monomer called chloroprene.b. Its IUPAC name is 2-chloro- 1, 3-butadiena.c. The term diena means that this molecule contains two double bonds.d. When these molecules polymerise they form the synthetic rubber

polymer called neoprene.


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9.5..GLASS AND CERAMICS

9.5.1 Glass

o The major component of glass is silica or silicon dioxide, SiO2 which found insand.

o Properties of glass: Transparent, hard but brittle, chemically inert, heatinsulator, electrical insulator, impermeable to liquid.

Glass

Fused glass (SiO)

Highly heat-resistant

glass

High transparency

High melting point

Resistant to chemical

attack

Uses : Laboratory

glassware, lenses,

telescope, mirrors

Lead crystal glass

(SiO, NaO, PbO, KO,

AlO)

Soft and easy to

melt.

High density

High refractive index

Uses- Lead crystal

glassware, art

objects, lens, prisms

and chandeliers

Borosilicate glass

(SiO, NaO, CaO,

AlO,BO)

Low thermal

expansion

coefficient

Resistant to heat and

chemical attack High melting point

Uses : Cooking

utensils, laboratory

glassware,

automobile

headlights

Soda-lime glass

(SIO, NA, CaO)

Good chemical

durability

High thermal

expansion

coefficient

Easy to make into

different shapes

Low melting point

Uses Bottles,

window panes,

mirrors, electrical

bulbs, flat glass

and all kind of glass

containers


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9.5.3 Ceramics Ceramics are made from clay, for example kaolin, a hydrated aluminium

silicate, AlO.2SiO.2HO.

When the clay is heated to a very high temperature, they undergo a series ofchemical reaction and are hardened permanently to form ceramics.

Ceramics are very hard, brittle, have a very high melting point, chemicallyinert and do not corrode.

The are good insulators of electricity and heat. Uses of ceramics: construction materials bricks, tiles, cement and pipes Ornamental articles bowls, cups, plates, vase and porcelain Electrical insulators spark plugs, fuses, insulators in electric iron and oven Superconductors

9.5 Uses of Composite Materialso Composite materials is a structural material that is formed by combining two or

more different substance such as metal, alloys, glass, ceramics and polymers.

o The resulting material has properties that are superior than those of the originalcomponents.

o Composite materials are created for specific application.


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Chemistry Chapter 9 Form 4 manufactured substances in industry

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Transcript of Chemistry Chapter 9 Form 4 manufactured substances in industry