Industry

Class 12 Chemistry, unit 23, book pages 344–353

Practise 28 MCQs Take the unit quiz Review 49 cards

Industrial chemistry turns raw materials from air, water, rocks and living things into the fuels, fertilizers, plastics, medicines, cement and food products that modern life depends on. This unit describes where these raw materials come from (with Pakistan's own resources), the key industrial processes and their conditions, addition and condensation polymerization, petrochemicals, cosmetics, cement and food chemistry, and the safety measures that protect workers and the environment.

Learning outcomes (5)

Justify the importance and significance of industrial chemistry in various industries such as manufacturing, energy, healthcare and environmental protection.
Describe the chemical processes involved in industrial production, including addition and condensation polymerization, and the properties and uses of the resulting materials.
Identify the raw materials and resources used in industrial chemistry, including those readily available in the context of Pakistan.
Explain the applications of industrial chemistry in industries such as petrochemical, cosmetics, cement, food production and more.
Elaborate on the safety measures and precautions necessary in industrial chemical processes and facilities.

Importance of industrial chemistryOften examined

The chemical industry is the ultimate fruit of chemical research. It changes cheap raw materials into useful products on a large scale and supplies them either directly to consumers or to other industries. Industrial chemists keep developing new processes, or improving old ones, to make them more energy efficient, to reduce the number of production steps and to lower their environmental impact.

Why industrial chemistry is important
Field	Role of industrial chemistry	Examples
Manufacturing	large-scale production of materials	plastics, synthetic fibres, elastomers (rubbers), paints, varnish, glass, cement, metals
Agriculture and food	fertilizers and pesticides have raised crop yields many times; new methods improve food and its quality	urea, DAP, insecticides, preservatives
Energy	refining petroleum, producing fuels and hydrogen	petrol, diesel, synthesis gas, biofuels, methanol
Healthcare	pharmaceuticals: medicines tailored by medicinal chemists with greater efficacy and safety	antibiotics, analgesics, vaccines
Personal care	better products than ever	soaps, shampoos, skin care products, hair dyes, cosmetics
Environmental protection	green chemistry: environment-friendly chemicals, waste management, recycling, biodegradable fibres	biodegradable plastics, catalytic converters, water treatment

Many chemical industries such as sulphuric acid, paints, varnish, metallurgy, cement, glass, petrochemicals, ammonia, fertilizers, pesticides and food materials are essential for modern life. Synthetic fibres are a major advance used for textiles and insulation.

Green chemistry: The branch of chemistry that designs processes and products which reduce or remove the use and production of hazardous substances, and develops waste management, recycling and biodegradable materials.

23.1Raw materials and their resources for chemical industryOften examined

All raw materials of the chemical industry come from the environment, which has four parts: the atmosphere (air), the hydrosphere (water), the biosphere (living things) and the lithosphere (rocks and soil).

Sources of industrial raw materials
Part of environment	Raw materials	Industrial use
Atmosphere	nitrogen, oxygen, hydrogen, carbon dioxide, noble gases	$N X_{2}$ and $H X_{2}$ make ammonia and then urea; $N X_{2}$ and $O X_{2}$ give nitrogen oxides and nitric acid; $O X_{2}$ for steel industry and hospitals; argon for welding
Hydrosphere	dissolved minerals in sea water: sodium, potassium, magnesium, calcium, sulphates, chlorides, bromides	common salt, caustic soda, chlorine, magnesium, bromine
Biosphere	cellulose, starch, oils, alkaloids, terpenes, resins; biomass; enzymes from microorganisms	paper from cellulose; food and chemicals from starch and oils; biogas and bioplastics from biomass; enzymes as biocatalysts in fermentation; medicines from plants and animals
Lithosphere	fossil fuels (petroleum, coal, natural gas); ores of iron, aluminium, sulphur, gold, chromium, uranium; limestone, gypsum, rock salt	fuels and petrochemicals; metals; cement; glass

The lithosphere provides the widest variety and largest mass of chemical raw materials. Unlike the other parts of the environment, its resources differ from one region to another. It is the source of elements such as oxygen, silicon, aluminium, iron, titanium and carbon. Its most useful raw materials are the fossil fuels.

23.2Chemical raw materials in Pakistan

Pakistan has a good range of mineral and fuel resources that can support its chemical industry.

Chemical raw materials of Pakistan
Resource	Facts from the book	Use
Iron ore	reserves about 1.427 billion tonnes	iron and steel
Chromite (ore of chromium)	Pakistan is an exporter	stainless steel, chrome plating
Gold and copper	large reserves in Balochistan (Saindak, Reko Diq), explored but largely unexploited	metals, electrical wires
Natural gas	large reserves, for example at Sui	fuel, fertilizer (ammonia, urea)
Coal	about 185 billion tonnes, with high sulphur content (mostly lignite at Thar)	power generation, fuel
Gypsum	about 5.5 billion tonnes	mainly cement manufacturing, plaster
Limestone, rock salt, marble, granite	widely found; rock salt from Khewra	cement, soda ash, caustic soda, construction
Gemstones (north of Pakistan)	aquamarine, tourmaline, peridot, emerald, ruby, topaz, zircon, rhodochrosite	jewellery; some serve as ores of precious metals

23.3Safety measures and precautions in chemical industryOften examined

Chemical safety is the set of methods and practices used to avoid accidents and to protect workers and the environment in a chemical industry. Its main purpose is to identify, evaluate and mitigate (reduce) dangerous situations during chemical processes. Typical hazards are explosive reactions, fire, and the release of toxic gases or chemicals.

Safety measures

Adopting guidelines: follow the rules of regulatory bodies such as OSHA (Occupational Safety and Health Administration) for proper storage, handling, use and disposal of hazardous chemicals.
Safety training: train every worker in process safety before giving a task; repeat training when the duty place or the process changes, so workers can protect themselves and others.
Robust engineering controls: automatic and efficient ventilation, safe building structures, and automated safety systems (alarms, pressure relief valves, sprinklers) reduce the risk of major damage.
Proper maintenance: critical processes need mechanical integrity and timely maintenance to prevent failures and leaks.
Management of change: a clear policy for changing chemicals, procedures, equipment and personnel reduces accidents caused by old, expired or worn-out equipment and chemicals.
Hazard assessment: regular hazard analysis, frequent review of process safety and investigation of every incident.
Emergency response: a complete emergency plan with fire fighting, first aid, evacuation routes and drills.

Precautions for workers

Wear personal protective equipment (PPE): goggles, gloves, lab coats, helmets, masks and respirators.
Read labels and safety data sheets (SDS) before handling a chemical; store incompatible chemicals separately.
Never eat or smoke in the plant; keep fire extinguishers, eye-wash stations and safety showers ready.

23.4Important chemical processesOften examined

The book lists thirteen important industrial processes. The table summarises them; the most examinable ones are given below with their equations and conditions.

Important industrial processes
Process	Conditions	Key equation	Product
Calcination	strong heating of limestone	$CaCO X_{3} 900 X^{\circ} C CaO + CO X_{2}$	quicklime for cement, glass, steel
Steam reforming	hydrocarbon + steam over Ni, about $80 0^{\circ} C$	$CH X_{4} + H X_{2} O CO + 3 H X_{2}$	hydrogen, ammonia, methanol
Catalytic reforming	naphtha over Pt catalyst, about $50 0^{\circ} C$	$C X_{7} H X_{16} C X_{6} H X_{5} CH X_{3} + 4 H X_{2}$	high octane petrol
Smelting	metal oxide + coke in a furnace	$Fe X_{2} O X_{3} + 3 CO 2 Fe + 3 CO X_{2}$	iron, zinc, tin, lead
Hall–Héroult	electrolysis of $Al X_{2} O X_{3}$ in molten cryolite, $95 0^{\circ} C$	$2 Al X_{2} O X_{3} + 3 C 4 Al + 3 CO X_{2}$	aluminium
Bessemer	air blown through molten pig iron	$2 C + O X_{2} 2 CO$ , $Si + O X_{2} SiO X_{2}$	steel
Haber	Fe catalyst, $45 0^{\circ} C$ , 200 atm	$N X_{2} + 3 H X_{2} 2 NH X_{3}$	ammonia, then urea
Bosch	steam over red hot coke, then shift over $Fe X_{2} O X_{3}$	$C + H X_{2} O CO + H X_{2}$	hydrogen
Frasch	superheated water pumped into sulphur beds	physical melting (sulphur melts at $11 5^{\circ} C$ )	sulphur
Downs	electrolysis of molten $NaCl + CaCl X_{2}$ at $60 0^{\circ} C$	$2 NaCl 2 Na + Cl X_{2}$	sodium and chlorine
Solvay	brine + $NH X_{3}$ + $CO X_{2}$	$NaCl + NH X_{3} + CO X_{2} + H X_{2} O NaHCO X_{3} + NH X_{4} Cl$	soda ash $Na X_{2} CO X_{3}$
Bergius	coal + $H X_{2}$ , Fe catalyst, $45 0^{\circ} C$ , 200 atm or more	$n C + (n + 1) H X_{2} \to C_{n} H_{2 n + 2}$	synthetic fuels, lubricants
Contact	$V X_{2} O X_{5}$ catalyst, $45 0^{\circ} C$ , 1 to 2 atm	$2 SO X_{2} + O X_{2} 2 SO X_{3}$	sulphuric acid

1. Polymerization

Small molecules called monomers join to form long-chain molecules called polymers. It is described fully in the next section.

2. Calcination

Limestone is strongly heated in a kiln and decomposes into calcium oxide (quicklime) and carbon dioxide. This is the first chemical change in cement and lime manufacture.

CaCO X_{3} 900 X^{\circ} C CaO + CO X_{2} ↑

3. Reforming

Petroleum fractions are converted into different products. In steam reforming hydrocarbons react with steam over a nickel catalyst to give hydrogen (synthesis gas), which is then used to make ammonia and methanol. In catalytic reforming straight-chain hydrocarbons are heated with a platinum catalyst to form branched and aromatic hydrocarbons, which give high octane petrol.

CH X_{4} + H X_{2} O Ni 800 X^{\circ} C CO + 3 H X_{2}

steam reforming

CO + 2 H X_{2} Cu / ZnO 250 X^{\circ} C, 50 atm CH X_{3} OH

methanol

CH X_{3} (CH X_{2}) X_{5} CH X_{3} Pt / Al X_{2} O X_{3} 500 X^{\circ} C C X_{6} H X_{5} CH X_{3} + 4 H X_{2}

catalytic reforming: heptane to toluene

4. Smelting

Metal oxides are heated with coke (carbon), which reduces them to the metal. In the blast furnace, coke burns to carbon monoxide, which reduces iron ore:

2 C + O X_{2} 2 CO; Fe X_{2} O X_{3} + 3 CO 2 Fe + 3 CO X_{2}

5. Hall–Héroult process

Aluminium is obtained by electrolysis of pure alumina ( $Al X_{2} O X_{3}$ ) dissolved in molten cryolite ( $Na X_{3} AlF X_{6}$ ) at about $95 0^{\circ} C$ . Cryolite lowers the melting point from about $205 0^{\circ} C$ and makes the melt conduct. Carbon lines the cell (cathode) and carbon blocks are the anodes.

Cathode: Al X^{3 +} + 3 e X^{-} Al Anode: 2 O X^{2 -} O X_{2} + 4 e X^{-}

2 Al X_{2} O X_{3} + 3 C 4 Al + 3 CO X_{2}

overall (anodes burn away)

6. Bessemer process

Hot air is blown through molten pig iron in a Bessemer converter. Oxygen removes the impurities (carbon, silicon, manganese) as gases or slag, giving steel. Carbon is then added in the correct amount.

2 C + O X_{2} Si + O X_{2} 2 Mn + O X_{2} MnO + SiO X_{2} 2 CO ↑ SiO X_{2} 2 MnO MnSiO X_{3} (slag)

7. Haber process

Nitrogen (from air) and hydrogen (from natural gas) combine over an iron catalyst. The reaction is reversible and exothermic, so a compromise temperature of about $45 0^{\circ} C$ and a high pressure of about 200 atm are used. Ammonia is then used to make urea fertilizer.

N X_{2} + 3 H X_{2} Fe catalyst 450 X^{\circ} C, 200 atm 2 NH X_{3} Δ H = - 92 kJ mo l^{- 1}

2 NH X_{3} + CO X_{2} NH X_{2} COONH X_{4} CO (NH X_{2}) X_{2} + H X_{2} O

urea

8. Bosch process

Steam is passed over red hot coke to give water gas. Water gas is mixed with more steam and passed over an iron oxide catalyst, which converts CO into $CO X_{2}$ and more hydrogen. $CO X_{2}$ is removed by dissolving it in water under pressure, leaving hydrogen.

C + H X_{2} O 1000 X^{\circ} C water gas CO + H X_{2}

CO + H X_{2} + H X_{2} O Fe X_{2} O X_{3} / Cr X_{2} O X_{3} 450 X^{\circ} C CO X_{2} + 2 H X_{2}

9. Frasch process

Sulphur is extracted from deep underground deposits by drilling three concentric pipes. Superheated water (about $16 5^{\circ} C$ , under pressure) is pumped down the outer pipe and melts the sulphur (m.p. about $11 5^{\circ} C$ ). Hot compressed air pushed down the inner pipe forces the molten sulphur up the middle pipe. The process is physical: no chemical reaction takes place.

10. Downs process

Sodium metal is obtained by electrolysis of molten halite (NaCl) mixed with calcium chloride, which lowers the melting point from $80 1^{\circ} C$ to about $60 0^{\circ} C$ . The cell has a graphite anode and a circular iron cathode.

Cathode: Na X^{+} + e X^{-} Na Anode: 2 Cl X^{-} Cl X_{2} + 2 e X^{-}

11. Solvay process

Sodium carbonate (soda ash) is made from brine (NaCl) and limestone, with ammonia recycled.

NaCl + NH X_{3} + CO X_{2} + H X_{2} O NaHCO X_{3} ↓ + NH X_{4} Cl

2 NaHCO X_{3} Δ Na X_{2} CO X_{3} + H X_{2} O + CO X_{2}

CaCO X_{3} CaO + H X_{2} O Ca (OH) X_{2} + 2 NH X_{4} Cl CaO + CO X_{2} Ca (OH) X_{2} CaCl X_{2} + 2 NH X_{3} + 2 H X_{2} O

recovery of ammonia

CaCO X_{3} + 2 NaCl Na X_{2} CO X_{3} + CaCl X_{2}

overall

12. Bergius process

Powdered coal is hydrogenated at high temperature and pressure with an iron catalyst to make synthetic petrol, diesel and lubricants.

n C + (n + 1) H X_{2} Fe catalyst 450 X^{\circ} C, 200 atm C X_{n} H X_{2 n + 2}

13. Contact process

Sulphur dioxide is oxidised to sulphur trioxide over vanadium(V) oxide. $SO X_{3}$ is absorbed in concentrated $H X_{2} SO X_{4}$ to give oleum, which is diluted with water. $SO X_{3}$ is not added directly to water because it forms a fine mist of acid.

S + O X_{2} SO X_{2}

2 SO X_{2} + O X_{2} V X_{2} O X_{5} 450 X^{\circ} C, 1 - 2 atm 2 SO X_{3} Δ H = - 197 kJ mo l^{- 1}

SO X_{3} + H X_{2} SO X_{4} H X_{2} S X_{2} O X_{7}; H X_{2} S X_{2} O X_{7} + H X_{2} O 2 H X_{2} SO X_{4}

23.4Polymerization: addition and condensationOften examined

Polymerization is a process in which small molecules (monomers) such as ethene, propene, butadiene, vinyl chloride and styrene link together under a set of conditions to form long-chain, high molecular mass compounds called polymers. The repeating part of the chain is the repeat unit.

Addition polymerization

In addition polymerization, unsaturated monomers (with a \ce{C=C} double bond) add to one another without the loss of any small molecule. The polymer has the same empirical formula as the monomer. It usually goes by a free radical chain mechanism started by an initiator such as a peroxide.

\ce{$n$ CH2=CH2 ->[\text{peroxide}][200^\circ C,\ 1000-2000\ atm] -(CH2-CH2)_{$n$}\bond{-}}

polyethene (LDPE)

Free radical mechanism of addition polymerization

Initiation: the initiator splits into free radicals, and a radical adds to one carbon of the double bond, making a new radical.
\ce{R-O-O-R -> 2RO.};\quad \ce{RO. + CH2=CH2 -> RO-CH2-CH2.}
Propagation: the new radical adds to another monomer, and this repeats thousands of times, so the chain grows.
\ce{RO-CH2-CH2. + CH2=CH2 -> RO-CH2CH2CH2CH2.}
Termination: two growing radicals join (or transfer an H atom), which stops the chain.
\ce{R'. + R''. -> R'-R''}

Low density polyethene (LDPE) is made at high pressure and has branched chains. High density polyethene (HDPE) is made at low pressure (a few atm, 60^\circ\mathrm{C}) with a Ziegler–Natta catalyst (\ce{TiCl4} + \ce{Al(C2H5)3}) and has straight chains that pack closely, so it is harder and stronger.

Common addition polymers
Polymer	Monomer	Properties	Uses
Polyethene (PE)	ethene \ce{CH2=CH2}	tough, flexible, waterproof, chemically inert	carrier bags, films, bottles, pipes
Polypropene (PP)	propene \ce{CH2=CHCH3}	stronger and more heat-resistant than PE	ropes, crates, carpets, car parts
Polyvinyl chloride (PVC)	vinyl chloride \ce{CH2=CHCl}	hard and rigid, flexible with plasticizer, fire-resistant	water pipes, window frames, cable insulation, raincoats
Polystyrene (PS)	styrene \ce{CH2=CHC6H5}	light, brittle; foamed form insulates	packaging, disposable cups, insulation
Teflon (PTFE)	tetrafluoroethene \ce{CF2=CF2}	very inert, non-stick, heat-resistant	non-stick pans, seals, insulation
Polyacrylonitrile (orlon)	acrylonitrile \ce{CH2=CHCN}	soft fibre like wool	sweaters, blankets

\ce{$n$ CH2=CHCl ->[\text{peroxide}] -(CH2-CHCl)_{$n$}\bond{-}}

PVC

vinyl chloride

PVC repeat unit

styrene

Condensation polymerization

In condensation polymerization, monomers with two functional groups each (for example \ce{-COOH}, \ce{-NH2}, \ce{-OH}) react with each other and a small molecule such as water or HCl is lost at every link. The polymer's formula is therefore not a simple multiple of the monomers.

Nylon-6,6

Hexanedioic acid (adipic acid) and hexane-1,6-diamine (hexamethylene diamine) are heated together. Each \ce{-COOH} reacts with an \ce{-NH2} to form an amide link \ce{-CONH-} and water. The name 6,6 shows that each monomer has 6 carbon atoms.

\ce{$n$ HOOC(CH2)4COOH + $n$ H2N(CH2)6NH2 ->[\Delta] -[OC(CH2)4CONH(CH2)6NH]_{$n$}\bond{-} + 2$n$ H2O}

adipic acid

hexamethylene diamine

nylon-6,6 repeat unit

Properties and uses: strong, tough, elastic and resistant to abrasion; used for textile fibres, ropes, fishing nets, parachutes, tyre cords, carpets and machine parts such as gears.

Polyester (PET, terylene)

Benzene-1,4-dicarboxylic acid (terephthalic acid) condenses with ethane-1,2-diol (ethylene glycol) to form ester links \ce{-COO-}.

\ce{$n$ HOOC-C6H4-COOH + $n$ HOCH2CH2OH -> -[OC-C6H4-COOCH2CH2O]_{$n$}\bond{-} + 2$n$ H2O}

Uses: clothing fibres (often mixed with cotton), drink bottles, films and food packaging.

Kevlar

Kevlar is an aromatic polyamide (aramid). It is made by condensation of benzene-1,4-diamine (p-phenylenediamine) with benzene-1,4-dicarbonyl chloride (terephthaloyl chloride), or with benzene-1,4-dicarboxylic acid, with loss of HCl (or water).

\ce{$n$ H2N-C6H4-NH2 + $n$ ClOC-C6H4-COCl -> -[HN-C6H4-NHCO-C6H4-CO]_{$n$}\bond{-} + 2$n$ HCl}

benzene-1,4-diamine

terephthaloyl chloride

Kevlar repeat unit

The rigid benzene rings keep the chains straight, and strong hydrogen bonds between \ce{C=O} and \ce{N-H} groups of neighbouring chains hold them in sheets. So Kevlar is about five times stronger than steel of the same mass, light, heat-resistant and flame-resistant.

Uses: bulletproof vests, helmets, fire-resistant clothing, tyres, ropes and cables, aircraft and boat parts, and sports equipment (rackets, helmets).

Comparison

Addition polymerization	Condensation polymerization
monomers are unsaturated (\ce{C=C})	monomers have two functional groups
no by-product; all atoms of monomer are in polymer	a small molecule (\ce{H2O}, HCl) is lost at each link
polymer has the same empirical formula as the monomer	polymer formula differs from the monomers
usually a chain (free radical) mechanism with an initiator	step-wise reaction between functional groups
examples: polyethene, PVC, polystyrene, Teflon	examples: nylon-6,6, polyester, Kevlar, bakelite

23.5PetrochemicalsOften examined

The chemical sector includes the businesses that create and manufacture industrial, specialised and other types of chemicals. Its largest branch is the petrochemical industry.

Petrochemicals: Compounds derived from petroleum (and natural gas) and its fractions. They are used to make insulation, soaps, detergents, paints, fertilizers, rubber, coatings, cosmetics and textiles.

There are three types of petrochemicals based on the starting materials: olefins, aromatics and synthesis gas.

a. Olefins

Olefins (alkenes) are obtained by cracking petroleum fractions. The major olefins are ethene, propene and butadiene; each is used to prepare many petrochemicals.

ethene

propene

1,3-butadiene

Petrochemicals obtained from ethylene (redrawn from the book's flow sheet).

\begin{aligned}\ce{2CH2=CH2 + O2 &->[Ag][250^\circ C] 2C2H4O}\ (\text{ethylene oxide})\\\ce{C2H4O + H2O &-> HOCH2CH2OH}\end{aligned}

ethylene glycol

\ce{CH2=CH2 + Cl2 -> ClCH2CH2Cl ->[500^\circ C] CH2=CHCl + HCl}

vinyl chloride

Petrochemicals obtained from propylene
Route from propene	Product
polymerization	polypropylene (PP)
ammoxidation (with \ce{NH3} and \ce{O2})	acrylonitrile (for acrylic fibres)
with HCN: acetone cyanohydrin, then esterification	methyl methacrylate (MMA, for Perspex)
oxidation to acrolein, then oxidation	acrylic acid and acrylic esters
oxidation	acetone
chlorohydrination, saponification	propylene oxide, then propylene glycol by hydration
peroxidation of ethylbenzene, then epoxidation	propylene oxide and styrene
hydration	isopropyl alcohol
oxo reaction (with CO and \ce{H2})	butanols (isobutanol) and octanol

Butadiene is used mainly to make synthetic rubbers such as styrene-butadiene rubber (SBR) for tyres, and nylon intermediates.

b. Aromatics

Aromatics include benzene, toluene and xylenes (BTX). They are obtained from cracked petrol and catalytic reforming, and are used to prepare many other compounds and polymers.

benzene

toluene

p-xylene

Compounds obtained from benzene, toluene and xylenes
Starting aromatic	Route	Product and use
benzene	alkylation with ethene, then dehydrogenation	ethylbenzene, then styrene, then polystyrene
benzene	hydrogenation to cyclohexane, oxidation, oximation, Beckmann rearrangement	caprolactam, the monomer of nylon-6
benzene	alkylation with propene, then oxidation	cumene, then phenol and acetone; these condense to bisphenol A (for polycarbonates, epoxy resins)
benzene	nitration, then hydrogenation	nitrobenzene, then aniline; with formaldehyde and phosgene gives MDI (for polyurethanes)
benzene	oxidation	maleic anhydride
toluene	nitration, hydrogenation, phosgenation	dinitrotoluene, toluene diamine, toluene diisocyanate (TDI, for polyurethane foam)
toluene	oxidation	phenol
p-xylene	oxidation, then with ethylene glycol	terephthalic acid, then polyester fibre and PET resin
o-xylene	oxidation	phthalic anhydride (plasticizers, dyes)
m-xylene	oxidation; or ammoxidation and hydrogenation	isophthalic acid; meta-xylenediamine

c. Synthesis gas

Synthesis gas (syn gas) is a mixture of carbon monoxide and hydrogen, with some nitrogen and hydrocarbons. It is made by steam reforming of natural gas or by gasification of coal and biomass.

\ce{CH4 + H2O ->[Ni][800^\circ C] CO + 3H2}

It is used to prepare ammonia and urea, methanol (and from it acetic acid), synthetic natural gas (SNG), and biofuels such as methanol and ethanol.
It is used to generate electricity and heat in combined heat and power (CHP) systems.
Gasification plants make it easy to separate \ce{CO2} for carbon capture, which helps reduce the greenhouse effect.

\ce{CO + 2H2 -> CH3OH};\qquad \ce{CH3OH + CO ->[\text{Rh or Ir catalyst}] CH3COOH}

23.5Cosmetics

Cosmetics are mixtures of chemical compounds derived from both natural and synthetic sources. They are used for personal and skin care, to conceal spots and to enhance natural looks; make-up can add colour to the face or change its appearance completely. Examples are lipstick, mascara, nail polish, creams, colours and dyes.

1. Nail polish

There is no single fixed formula for nail polish, but it has four basic types of ingredient:

Raw materials of nail polish
Component	Examples	Function
Film forming agent	nitrocellulose, cellulose acetate, cellulose acetate butyrate, vinyl polymers, acrylates, maleic acid monobutyl ester, zein (a protein)	forms the hard, shiny film on the nail
Resins and plasticizers	castor oil, amyl and butyl stearate, mixtures of fatty acids and glycerol	make the film flexible and help it stick, so it does not crack
Solvents	ethyl acetate, butyl acetate, acetone, toluene, isopropyl alcohol	dissolve the other components and evaporate quickly so the polish dries
Colouring agents	iron oxides, colour lakes, mica, titanium dioxide, carmine, ultramarine, manganese violet	give colour and shine

ethyl acetate

acetone

Manufacturing method

The pigments are mixed with nitrocellulose and plasticizer and ground in a two-roll differential speed mill to give a fine dispersion of colour.
When fully milled, the mixture is removed as sheets, which are broken into small chips for mixing with the solvent.
The mixture is cooled slightly before adding other materials such as perfumes, moisturizers and cooling agents.
The mixture is pumped into smaller drums and taken to the production line, where it is filled through explosion-proof pumps into small bottles for sale (the solvents are highly flammable).

2. Lipstick

Raw materials of lipstick
Raw material	Examples
Waxes	beeswax, carnauba wax, candelilla wax
Oils	lanolin oil, castor oil, vegetable oils
Natural ingredients	butter, natural pigments, fruit-based chemicals
Pigments	natural and synthetic
Alcohols	isopropyl alcohol
Preservatives	antioxidants

Manufacturing method

Because the ingredients are of different kinds, three mixtures are first melted and mixed separately: one of solvents, one of oils, and one of fats and waxy materials.
The solvent mixture and the oils are mixed with the colour pigments, and this pigment mass is ground.
The ground pigment mass is added to the hot wax mass and stirred until a uniform colour is obtained; the mass is then made free from air.
The melted mass is poured into a mould held upside down, cooled, separated from the mould and sealed from the bottom.
The lipsticks are passed quickly through a flame to seal pinholes and improve the finish; then they are capped, labelled and packed.

23.5CementOften examined

Cement is a very useful material used to glue bricks and stones together in construction after mixing with water, sand and crushed stone. It is a greenish-grey powder (the book calls it a dirty green coloured powder). The common type is Portland cement.

Raw materials

Raw materials of cement
Raw material	Amount	Supplies
Limestone (\ce{CaCO3})	about 65%	calcium oxide (lime)
Clay or shale	20 to 30%	silica (\ce{SiO2}), alumina (\ce{Al2O3}), iron oxide
Gypsum (\ce{CaSO4.2H2O})	2 to 3%	added at the end to slow down (retard) setting
Supplementary ingredients	minor amounts	fly ash, silica fume, iron ore or mill scale, bauxite, according to the type of cement

Process

Mining: the factory is built near the raw materials to save transport cost. Limestone and clay are dug out and brought to the factory by trucks.
Crushing: the big stones are crushed to small pebbles and then ground to a fine powder.
Homogenisation: the powders are mixed in the correct proportions and blended thoroughly to give a uniform powder called raw meal.
Clinkerization: the raw meal is heated in a rotary kiln at about 1400 to 1450^\circ\mathrm{C}. Limestone first decomposes to CaO, which then reacts with silica, alumina and iron oxide to form silicates, aluminates and ferrites. These form small, semi-round pebbles called clinker.
Cement grinding: the cooled clinker is ground in a ball mill with 2 to 3% gypsum (to increase the setting time) and other additives, giving cement.
Packing: cement is packed in 50 kg bags, or sent in bulk by open trucks.

Flow sheet of cement manufacture (redrawn from the book).

Reactions in the kiln

\ce{CaCO3 ->[900^\circ C] CaO + CO2}

calcination

\begin{aligned}\ce{2CaO + SiO2 &-> Ca2SiO4}\quad(\text{dicalcium silicate})\\\ce{3CaO + SiO2 &-> Ca3SiO5}\quad(\text{tricalcium silicate})\end{aligned}

\begin{aligned}\ce{3CaO + Al2O3 &-> Ca3Al2O6}\quad(\text{tricalcium aluminate})\\\ce{4CaO + Al2O3 + Fe2O3 &-> Ca4Al2Fe2O10}\quad(\text{tetracalcium aluminoferrite})\end{aligned}

23.7Industrial chemistry in food production

Industrial chemistry helps to produce, process, preserve and package food on a large scale.

1. Food additives and preservatives

Food additives
Additive	Function	Example
Anti-caking agents	stop powdered ingredients from becoming lumpy	calcium silicate in table salt
Antioxidants	prevent foods from oxidising or becoming rancid	vitamin C, BHA, BHT
Artificial sweeteners	sweeten without sugar	aspartame, saccharin
Food acids	maintain the correct acid level (taste, safety)	citric acid, acetic acid
Synthetic colours	enhance the colour of food	tartrazine
Preservatives	stop growth of bacteria and moulds	sodium benzoate

sodium benzoate

citric acid

2. Fermentation

Fermentation is a process that uses microorganisms and their enzymes to convert raw materials into finished edible products such as vinegar, wine, yoghurt, cheese and bread. For example, yeast turns glucose into ethanol, and acetic acid bacteria oxidise ethanol to vinegar:

\ce{C6H12O6 ->[\text{zymase (yeast)}] 2C2H5OH + 2CO2}

\ce{C2H5OH + O2 ->[\text{\textit{Acetobacter}}] CH3COOH + H2O}

vinegar

3. Food processing

Food processing is the technique of transforming food items into a form that can be consumed, through different physical and chemical steps: for example milling wheat into flour, hydrogenating vegetable oil into ghee, pasteurising milk and canning fruit.

\text{vegetable oil }(\ce{C=C}) + \ce{H2 ->[Ni][150-200^\circ C]}\ \text{banaspati ghee}

hydrogenation

4. Purification

Many food and beverage products go through a purification step to remove coloured contaminants, unwanted taste and odour, for example decolourising sugar solution with activated charcoal, and purifying drinking water by filtration and chlorination.

5. Food packaging

Food packaging is a crucial step that uses special materials and techniques (plastic films, aluminium foil, tin-plated cans, vacuum and nitrogen-flushed packs) to protect food from biological and chemical attack and contamination.

6. Food waste management

Food industry waste is treated chemically with acids, bases, oxidisers or reducing agents to reduce its hazardous nature; organic waste can also be composted or converted into biogas.

Formula sheet

Calcination of limestone

\ce{CaCO3 ->[900^\circ C] CaO + CO2}

first step in cement and lime making

Haber process

\ce{N2 + 3H2 <=>[Fe][450^\circ C,\ 200\ atm] 2NH3}

exothermic, \Delta H=-92\,\mathrm{kJ\,mol^{-1}}

Urea from ammonia

\ce{2NH3 + CO2 -> NH2COONH4 -> CO(NH2)2 + H2O}

ammonium carbamate dehydrates to urea

Contact process

\ce{2SO2 + O2 <=>[V2O5][450^\circ C] 2SO3};\ \ce{SO3 + H2SO4 -> H2S2O7}

oleum is diluted to give sulphuric acid

Steam reforming

\ce{CH4 + H2O ->[Ni] CO + 3H2}

gives synthesis gas

Bosch process

\ce{C + H2O -> CO + H2};\ \ce{CO + H2O ->[Fe2O3] CO2 + H2}

hydrogen from coke and steam

Hall–Héroult process

\ce{Al^3+ + 3e- -> Al};\ \ce{2Al2O3 + 3C -> 4Al + 3CO2}

electrolysis of alumina in molten cryolite

Downs process

\ce{2NaCl(l) -> 2Na + Cl2}

electrolysis of molten NaCl with \ce{CaCl2}

Solvay process

\ce{NaCl + NH3 + CO2 + H2O -> NaHCO3 + NH4Cl};\ \ce{2NaHCO3 -> Na2CO3 + H2O + CO2}

soda ash from brine and limestone

Addition polymerization of ethene

\ce{$n$ CH2=CH2 -> -(CH2-CH2)_{$n$}\bond{-}}

no by-product

PVC

\ce{$n$ CH2=CHCl -> -(CH2-CHCl)_{$n$}\bond{-}}

addition polymer of vinyl chloride

Nylon-6,6

\ce{$n$ HOOC(CH2)4COOH + $n$ H2N(CH2)6NH2 -> -[OC(CH2)4CONH(CH2)6NH]_{$n$}\bond{-} + 2$n$ H2O}

condensation polymer with amide links

Kevlar

\ce{$n$ H2N-C6H4-NH2 + $n$ ClOC-C6H4-COCl -> -[HN-C6H4-NHCO-C6H4-CO]_{$n$}\bond{-} + 2$n$ HCl}

aromatic polyamide

Clinker formation

\ce{3CaO + SiO2 -> Ca3SiO5};\ \ce{3CaO + Al2O3 -> Ca3Al2O6}

in the rotary kiln at 1400 to 1450^\circ\mathrm{C}

Fermentation

\ce{C6H12O6 -> 2C2H5OH + 2CO2}

yeast enzymes (zymase)

Key terms

Industrial chemistry: The branch of chemistry that applies chemical knowledge to convert raw materials into useful products on a large scale.
Green chemistry: Chemistry aimed at environment-friendly chemicals and processes, waste management, recycling and biodegradable materials.
Raw materials: Natural substances (from the atmosphere, hydrosphere, biosphere and lithosphere) used by industry to make products.
Lithosphere: The solid outer part of the Earth; it supplies fossil fuels, ores and minerals, the largest variety of raw materials.
Chemical safety: The methods and practices used to avoid accidents in the chemical industry and to protect workers and the environment.
OSHA: Occupational Safety and Health Administration, a regulatory body whose guidelines cover storage, handling, use and disposal of hazardous chemicals.
Hazard assessment: Regular identification and evaluation of dangers in a process, with review of safety and investigation of incidents.
Calcination: Strong heating of an ore (such as limestone) below its melting point to decompose it: \ce{CaCO3 -> CaO + CO2}.
Reforming: Conversion of petroleum fractions into other products: steam reforming gives hydrogen; catalytic reforming gives high octane petrol.
Smelting: Heating a metal oxide with coke to reduce it to the metal.
Water gas: A mixture of CO and \ce{H2} made by passing steam over red hot coke.
Synthesis gas (syn gas): A mixture of carbon monoxide and hydrogen (with some nitrogen and hydrocarbons) used to make ammonia, methanol and fuels.
Monomer: A small molecule that joins with many others to form a polymer.
Polymer: A long-chain molecule of high molecular mass formed by joining many monomers.
Polymerization: The process in which monomers link together under a set of conditions to form a polymer.
Addition polymerization: Polymerization of unsaturated monomers by addition across \ce{C=C}, without loss of any molecule; for example polyethene and PVC.
Condensation polymerization: Polymerization between monomers with two functional groups in which a small molecule such as water or HCl is lost at each link; for example nylon-6,6.
Nylon-6,6: A polyamide made from adipic acid and hexamethylene diamine, each with 6 carbon atoms.
Kevlar: An aromatic polyamide (aramid) from benzene-1,4-diamine and terephthalic acid (or its chloride); very strong, used in bulletproof vests.
Petrochemicals: Compounds derived from petroleum and its fractions; classed as olefin-based, aromatics-based and synthesis gas-based.
Olefins: Alkenes obtained by cracking, mainly ethene, propene and butadiene.
Aromatics (BTX): Benzene, toluene and xylenes, used to make polymers, dyes, solvents and many chemicals.
Cosmetics: Mixtures of natural and synthetic compounds used for personal and skin care, to conceal spots and enhance appearance.
Film forming agent: The component of nail polish, such as nitrocellulose, that forms the hard glossy film.
Plasticizer: A substance added to a polymer or film to make it flexible and less brittle.
Cement: A greenish-grey powder made by heating limestone and clay and grinding the clinker with gypsum; it binds bricks and stones after mixing with water and sand.
Raw meal: The finely ground, homogenised mixture of limestone and clay fed into the cement kiln.
Clinker: Small, semi-round pebbles of calcium silicates, aluminates and ferrites formed in the rotary kiln.
Rotary kiln: A long, slightly sloping, rotating steel cylinder in which raw meal is heated to 1400 to 1450^\circ\mathrm{C}.
Food additive: A substance added to food to preserve it or improve its taste, colour or texture.
Anti-caking agent: An additive that stops powdered ingredients from becoming lumpy.
Antioxidant: A substance that prevents food from oxidising or becoming rancid.
Fermentation: A process that uses microorganisms and their enzymes to convert raw materials into edible products such as vinegar and wine.
Food processing: The transformation of raw food items into a consumable form by physical and chemical steps.

Multiple choice questionsp. 351

i1 mark

Industrial chemistry is very important in the field of:

AMedicines
BCement
CGlass
DAll of themAnswer

Why

Medicines (pharmaceutical industry), cement and glass are all produced on a large scale by industrial chemical processes, so all three options are correct.

ii1 mark

Halite (rock salt) in Pakistan is obtained from:

ALithosphereAnswer
BHydrosphere
CBiosphere
DAtmosphere

Why

In Pakistan, rock salt is mined from underground deposits in the Salt Range (Khewra mine), which is part of the lithosphere. Common salt can also come from sea water (hydrosphere), but halite is a mineral mined from rock.

iii1 mark

The methods and applications to avoid accidents in chemical industry is termed as:

ASecurity
BHazard analysis
CChemical safetyAnswer
DProtection

Why

The book defines chemical safety as the practices used to avoid accidents and to protect workers and the environment. Hazard analysis is only one part of chemical safety.

iv1 mark

Butadiene is included in the class:

AOlefinsAnswer
BAromatics
CPetroleum
DSyn gas

Why

Butadiene, \ce{CH2=CH-CH=CH2}, is an alkene (diene). The book names ethene, propene and butadiene as the major olefins. It has no benzene ring, so it is not an aromatic.

v1 mark

Polyvinyl chloride (PVC) is a polymer:

AAdditionAnswer
BSubstitution
CReduction
DCondensation

Why

PVC forms when vinyl chloride molecules add to one another across their \ce{C=C} bonds with no small molecule lost: n\,\ce{CH2=CHCl} \rightarrow \ce{-(CH2-CHCl)}_{n}\ce{-}.

vi1 mark

Nylon-6,6 preparation needs:

AAdipic acid
BHexamethylene diamine
CCitric acid
DBoth a and bAnswer

Why

Nylon-6,6 is a condensation polymer of adipic acid (hexanedioic acid) and hexamethylene diamine (hexane-1,6-diamine), each with 6 carbon atoms.

Note. The book prints \"Nylon 6'6\"; the correct name is nylon-6,6.

vii1 mark

The percentage of gypsum in cement is:

A2–3%Answer
B1–5%
C20%
D65%

Why

Only 2 to 3% gypsum is ground with the clinker to slow down setting. 65% is the share of limestone and 20 to 30% that of clay.

viii1 mark

Vinegar is made by:

AAddition polymerization
BCondensation polymerization
CFermentationAnswer
DPasteurization

Why

Vinegar is made by fermentation: yeast turns sugar into ethanol, and acetic acid bacteria then oxidise ethanol to acetic acid. Pasteurization only kills microbes by heating.

Short answer questionsp. 351

i3 marks

What are the petrochemicals? Explain their classes.

Solution

Petrochemicals are compounds derived from petroleum (and natural gas) and its fractions. They are used to make plastics, insulation, soaps, detergents, paints, fertilizers, rubber, coatings, cosmetics and textiles. They have three classes based on the starting material:

Olefins: alkenes such as ethene, propene and butadiene, obtained by cracking. Products: polyethene, PVC, polypropene, ethylene glycol, synthetic rubber.
Aromatics: benzene, toluene and xylenes (BTX). Products: styrene and polystyrene, phenol, nylon-6, polyester (PET), dyes.
Synthesis gas: a mixture of CO and \ce{H2}. Products: ammonia, urea, methanol, acetic acid, fuels.

ii3 marks

What useful products are obtained from ethylene?

Solution

Ethylene (ethene, \ce{CH2=CH2}) is the most important olefin. The book's flow sheet shows these products:

Polyethene (LDPE, HDPE, LLDPE) by polymerization, for bags, films and pipes.
Alpha-olefins by oligomerization, for detergents and plastics.
PVC: chlorination gives ethylene dichloride, which loses HCl to give vinyl chloride, which is polymerized.
Ethylene glycol (antifreeze, polyester) from ethylene oxide by hydration.
Acetic acid via acetaldehyde by oxidation.
Vinyl acetate, polyvinyl acetate and polyvinyl alcohol, and raw materials for other chemicals.

\ce{CH2=CH2 + Cl2 -> ClCH2CH2Cl ->[-HCl] CH2=CHCl}

iii3 marks

Enlist useful products obtained from benzene and its derivatives.

Solution

Benzene, toluene and xylenes (aromatics) give many useful products:

Starting compound	Useful products
Benzene	ethylbenzene, styrene, polystyrene; cyclohexane, caprolactam (nylon-6); cumene, phenol and acetone, bisphenol A; nitrobenzene, aniline, MDI (polyurethane); maleic anhydride
Toluene	dinitrotoluene, toluene diamine, toluene diisocyanate (TDI, for polyurethane foam); phenol
Xylenes	terephthalic acid from p-xylene, then polyester fibre and PET; phthalic anhydride from o-xylene; isophthalic acid from m-xylene

They are also used as raw materials for dyes, drugs, detergents and solvents.

iv3 marks

How does chemical industry get raw materials for production of useful stuff?

Solution

The chemical industry gets all its raw materials from the four parts of the environment:

Atmosphere: \ce{N2} and \ce{H2} for ammonia and urea, \ce{N2} and \ce{O2} for nitric acid, \ce{O2} for steel making and hospitals.
Hydrosphere: sea water gives salts of sodium, potassium, magnesium and calcium, and chlorides, sulphates and bromides.
Biosphere: plants give cellulose (paper), starch, oils, resins and alkaloids; biomass gives biogas and bioplastics; microorganisms give enzymes.
Lithosphere: the widest variety: fossil fuels (petroleum, coal, natural gas), metal ores, limestone, gypsum and rock salt.

v2026 Annual I, Set B, Q.2 (ix) OR3 marks

Explain the addition polymerization with an example.

Solution

Addition polymerization is the joining of many unsaturated monomer molecules (containing \ce{C=C}) to form a polymer without the loss of any small molecule. The \pi bond of each monomer opens and forms new single bonds to neighbouring monomers, so the polymer has the same empirical formula as the monomer. It usually goes by a free radical mechanism started by a peroxide initiator.

Example: vinyl chloride polymerizes to polyvinyl chloride (PVC), used for pipes and cable insulation:

\ce{$n$ CH2=CHCl ->[\text{peroxide}] -(CH2-CHCl)_{$n$}\bond{-}}

Other examples: polyethene from ethene, polystyrene from styrene, Teflon from \ce{CF2=CF2}.

vi3 marks

Explain condensation polymerization with an example.

Solution

Condensation polymerization is the joining of monomers that each have two functional groups, with the loss of a small molecule such as water or HCl at every link. The polymer's formula is therefore not a simple multiple of the monomers.

Example: adipic acid and hexamethylene diamine react to form nylon-6,6. Each \ce{-COOH} reacts with an \ce{-NH2} to form an amide link \ce{-CONH-} and water:

\ce{$n$ HOOC(CH2)4COOH + $n$ H2N(CH2)6NH2 -> -[OC(CH2)4CONH(CH2)6NH]_{$n$}\bond{-} + 2$n$ H2O}

Nylon-6,6 is strong and elastic and is used for fibres, ropes and tyre cords. Other examples: polyester (PET) and Kevlar.

vii2026 Annual I, Set D, Q.4 OR3 marks

How is the Kevlar prepared? What are its uses?

Solution

Preparation: Kevlar is an aromatic polyamide made by condensation polymerization of benzene-1,4-diamine (p-phenylenediamine) with benzene-1,4-dicarbonyl chloride (terephthaloyl chloride); HCl is lost at each amide link. Benzene-1,4-dicarboxylic acid can be used instead, with loss of water.

\ce{$n$ H2N-C6H4-NH2 + $n$ ClOC-C6H4-COCl -> -[HN-C6H4-NHCO-C6H4-CO]_{$n$}\bond{-} + 2$n$ HCl}

Rigid benzene rings and hydrogen bonds between chains make it very strong (about five times stronger than steel of the same mass), light and heat-resistant.

Uses: bulletproof vests and helmets, fire-resistant clothing, tyres, ropes and cables, aircraft parts and sports equipment.

viii3 marks

Write the raw materials used in nail polish.

Solution

Nail polish has no fixed formula, but its raw materials fall into four groups:

Film forming agents: nitrocellulose, cellulose acetate, cellulose acetate butyrate, vinyl polymers, acrylates, maleic acid monobutyl ester, zein (a protein). They form the hard shiny film.
Resins and plasticizers: castor oil, amyl and butyl stearate, mixtures of fatty acids and glycerol. They keep the film flexible.
Solvents: ethyl acetate, butyl acetate, acetone, toluene, isopropyl alcohol. They dissolve the solids and evaporate quickly.
Colouring agents: iron oxides, colour lakes, mica, titanium dioxide, carmine, ultramarine, manganese violet.

ix3 marks

Enlist the raw materials used for making lipstick.

Solution

Lipstick is a mixture of waxes, oils and pigments. Its raw materials are:

Waxes: beeswax, carnauba wax, candelilla wax (give shape and firmness).
Oils: lanolin oil, castor oil, vegetable oils (make it smooth and moisturise the lips).
Natural ingredients: butter, natural pigments, fruit-based chemicals.
Pigments: both natural and synthetic (give colour).
Alcohols: isopropyl alcohol (solvent).
Preservatives: antioxidants (stop the oils becoming rancid).

x3 marks

Write down the method for the preparation of lipstick.

Solution

Because the ingredients are different in nature, three mixtures are melted and mixed separately: solvents, oils, and fats with waxes.
The solvent mixture and the oils are mixed with the colour pigments, and the pigment mass is ground.
The ground pigment mass is added to the hot wax mass and stirred until the colour is uniform; air is removed from the mass.
The melted mass is poured into a mould held upside down, cooled, separated from the mould and sealed from the bottom.
The lipsticks are passed through a flame to seal pinholes and improve the finish, then capped, labelled and packed.

Long answer questionsp. 351

i7 marks

Write a detailed note on cement.

Solution

Introduction

Cement is a greenish-grey powder used to glue bricks and stones together in construction after mixing with water, sand and crushed stone. When water is added, its compounds react and harden into a stone-like mass. The common type is Portland cement. Pakistan has large deposits of limestone, clay and gypsum, so cement is a major industry here.

Raw materials

Raw material	Percentage	Role
Limestone (\ce{CaCO3})	about 65%	source of CaO
Clay or shale	20 to 30%	source of \ce{SiO2}, \ce{Al2O3}, \ce{Fe2O3}
Gypsum (\ce{CaSO4.2H2O})	2 to 3%	increases (retards) setting time
Supplementary ingredients	minor	fly ash, silica fume, iron ore or mill scale, bauxite

Manufacturing process

Mining: raw materials are dug near the factory and transported by trucks.
Crushing: big stones are crushed to pebbles and ground to fine powder.
Homogenisation: limestone and clay are mixed in the correct proportions to give a uniform raw meal.
Clinkerization: the raw meal is heated in a rotary kiln at 1400 to 1450^\circ\mathrm{C}. CaO combines with silica, alumina and iron oxide to form silicates, aluminates and ferrites, which form small semi-round pebbles called clinker.
Cement grinding: clinker is ground in a ball mill with 2 to 3% gypsum and other additives.
Packing: in 50 kg bags or bulk trucks.

Reactions in the kiln

\ce{CaCO3 ->[900^\circ C] CaO + CO2}

\begin{aligned}\ce{2CaO + SiO2 &-> Ca2SiO4}\\\ce{3CaO + SiO2 &-> Ca3SiO5}\\\ce{3CaO + Al2O3 &-> Ca3Al2O6}\end{aligned}

\ce{4CaO + Al2O3 + Fe2O3 -> Ca4Al2Fe2O10}

Flow sheet

Flow sheet of cement manufacture.

Setting and uses

With water the silicates and aluminates are hydrated and form interlocking crystals, so cement sets and hardens, even under water. Gypsum prevents it from setting too quickly. Cement is used for mortar, concrete and reinforced concrete in buildings, roads, bridges and dams.

ii7 marks

Write the involvement of industrial chemistry in food production and preservation.

Solution

Introduction

Industrial chemistry helps to grow, process, preserve and package food on a large scale, so that safe food reaches a growing population. In production, fertilizers (urea, DAP) and pesticides made by the chemical industry have raised crop yields many times.

1. Food additives and preservatives

Anti-caking agents stop powdered ingredients from becoming lumpy.
Antioxidants (vitamin C, BHT) prevent foods from oxidising or becoming rancid.
Artificial sweeteners (aspartame, saccharin) sweeten without sugar.
Food acids (citric acid, acetic acid) maintain the correct acid level.
Synthetic colours enhance the colour of food.
Preservatives such as sodium benzoate stop the growth of bacteria and moulds.

sodium benzoate

2. Fermentation

Microorganisms and their enzymes convert raw materials into edible products such as vinegar, wine, yoghurt, cheese and bread.

\begin{aligned}\ce{C6H12O6 &->[\text{yeast}] 2C2H5OH + 2CO2}\\\ce{C2H5OH + O2 &->[\text{bacteria}] CH3COOH + H2O}\end{aligned}

3. Food processing

Food items are transformed into consumable forms by physical and chemical steps, for example milling, pasteurisation of milk, canning, and hydrogenation of vegetable oil to ghee with a nickel catalyst.

4. Purification

A purification step removes coloured contaminants, unwanted taste and odour, for example decolourising sugar with activated charcoal and chlorinating drinking water.

5. Food packaging

Special materials (plastic films, aluminium foil, tin-plated cans) and techniques (vacuum and nitrogen packing) protect food from biological and chemical attack and contamination, which increases shelf life.

6. Food waste management

Waste is treated with acids, bases, oxidisers or reducing agents to reduce its hazardous nature, or converted into compost and biogas.

iii7 marks

Write a detailed account of petrochemicals.

Solution

Definition

Petrochemicals are compounds derived from petroleum (and natural gas) and its fractions. They are the raw materials for plastics, synthetic fibres, rubber, detergents, paints, fertilizers, coatings, cosmetics and textiles. Based on the starting material, they are of three types.

1. Olefins

The major olefins are ethene, propene and butadiene, obtained by cracking petroleum fractions.

From ethene: polyethene (LDPE, HDPE), alpha-olefins, PVC (via ethylene dichloride and vinyl chloride), ethylene oxide and ethylene glycol, acetaldehyde and acetic acid, vinyl acetate and polyvinyl alcohol.
From propene: polypropylene, acrylonitrile, methyl methacrylate, acrylic acid and esters, acetone, propylene oxide and propylene glycol, isopropyl alcohol, butanols and octanol.
From butadiene: synthetic rubbers such as SBR for tyres.

\begin{aligned}\ce{$n$ CH2=CH2 &-> -(CH2-CH2)_{$n$}\bond{-}}\\\ce{CH2=CH2 + Cl2 &-> ClCH2CH2Cl ->[-HCl] CH2=CHCl}\end{aligned}

2. Aromatics

Benzene, toluene and xylenes (BTX) come from catalytic reforming and cracked petrol.

Benzene: styrene and polystyrene; caprolactam (nylon-6); cumene, phenol and acetone, bisphenol A; aniline and MDI (polyurethanes); maleic anhydride.
Toluene: toluene diisocyanate (polyurethane foam), phenol, solvents.
Xylenes: terephthalic acid from p-xylene gives polyester fibre and PET bottles; phthalic anhydride from o-xylene; isophthalic acid from m-xylene.

benzene

toluene

p-xylene

3. Synthesis gas

Syn gas is a mixture of CO and \ce{H2} (with some \ce{N2} and hydrocarbons), made by steam reforming of natural gas. It is used to make ammonia, urea, methanol, acetic acid, SNG and biofuels, and to produce electricity and heat in combined heat and power systems.

\ce{CH4 + H2O ->[Ni] CO + 3H2};\qquad \ce{CO + 2H2 -> CH3OH}

Importance

Petrochemicals supply most of the plastics, fibres, rubbers, detergents and solvents of modern life, and fertilizers for agriculture. In Pakistan, natural gas is the main feedstock for the fertilizer industry.

Exam focus

Write a detailed note on cement: raw materials, process and kiln reactions. (long)
Book long question i; percentages (65%, 20 to 30%, 2 to 3%) and kiln temperature are MCQ favourites.
Go to answer
Petrochemicals and their three classes, with products from ethylene and benzene. (long)
Book long iii and short i to iii; butadiene is an olefin (MCQ iv).
Go to answer
Addition polymerization with an example (PVC or polyethene). (short)
The SLO names addition and condensation polymerization; the PVC equation was asked in FBISE 2026 Set B.
Go to answer
Condensation polymerization: nylon-6,6 and Kevlar equations and uses. (short)
Nylon-6,6 and Kevlar equations were asked in FBISE 2026 Set D Q.4 OR.
Go to answer
Important industrial processes: Haber, Contact, Solvay, Downs, Hall–Héroult with conditions. (short)
Equations with catalyst, temperature and pressure are common short questions.
Go to answer
Safety measures and precautions in the chemical industry. (short)
A full SLO; list the seven measures from the book.
Go to answer
Raw materials from the four spheres, and resources of Pakistan. (short)
Book short iv and MCQ ii; know Pakistan's figures (iron ore, coal, gypsum).
Go to answer
Industrial chemistry in food production and preservation. (long)
Book long ii; additives, fermentation and packaging.
Go to answer
Raw materials and manufacture of nail polish and lipstick. (short)
Three of ten book short questions are on cosmetics.
Go to answer
Importance of industrial chemistry in manufacturing, energy, healthcare and environmental protection. (short)
First SLO of the unit.
Go to answer