Chemical Industries – SS1 Chemistry Lesson Note (Third Term)

A chemical industry is an industry that uses chemical reactions to make useful chemicals from other substances called raw materials.

Behavioural objectives

1. Define a chemical industry.
2. List the important raw materials used in the chemical industry.
3. State the uses of nitrogen, ammonia and calcium trioxocarbonate (iv) as industrial raw materials.
4. State the products obtained from sea water and rock salt.
5. Name the sources of sulphur and the compounds made from it.
6. Name the main petrochemicals and some products made from them.

What is a raw material?

A raw material is a substance from which another useful product is made.

• Natural raw materials: taken from air, water, rocks, soil or underground, such as limestone and crude oil.
• Intermediate products: made in one industry and used as raw material in another, such as ammonia for fertilisers.
• Example: limestone is the raw material for lime and cement.

What are the raw materials of the chemical industry?

There are seven important raw materials of the chemical industry: air, calcium trioxocarbonate (iv), sea water and rock salt, sulphur, metallic mineral ores, coal, and natural gas and petroleum.

1. Air: source of oxygen and nitrogen.
2. CaCO₃: found as limestone, chalk and marble.
3. Sea water and rock salt: source of NaCl and NaBr.
4. Sulphur: native sulphur and sulphur-containing minerals.
5. Metallic mineral ores: source of metals.
6. Coal: source of coke, coal gas and coal tar.
7. Natural gas and petroleum: source of petrochemicals and fuels.

What are the sources and uses of each raw material?

Each raw material gives specific products, which are taught one by one below.

How is air used as a raw material?

Air is the chief source of oxygen (O₂) and nitrogen (N₂), which are separated from liquid air by fractional distillation.

• Nitrogen: used in the manufacture of ammonia (NH₃).
• Ammonia to acid: NH₃ is used to make trioxonitrate (v) acid.
• Uses of trioxonitrate (v) acid: making explosives, plastics and other materials.
• Ammonia to salts: NH₃ is used to make ammonium salts such as NH₄NO₃ and (NH₄)₂SO₄.
• Uses of ammonium salts: manufacture of fertilisers.

Ammonia is made from nitrogen and hydrogen with an iron catalyst:

• Equation: N₂ + 3H₂ → 2NH₃ (the reaction is reversible).

How is calcium trioxocarbonate (iv) (CaCO₃) used?

Calcium trioxocarbonate (iv) is the compound found in limestone, chalk and marble, and it is used to make lime, cement and sodium compounds.

• Forms: limestone, chalk and marble.
• Lime: heating CaCO₃ gives calcium oxide (lime) and CO₂.
• Cement and concrete: limestone and lime are used to make cement and concrete.
• Carbon dioxide: the CO₂ is used in the Solvay process to make sodium trioxocarbonate (iv).
• Baking powder: the Solvay process also gives sodium hydrogentrioxocarbonate (iv), a raw material for baking powder.

Equation for making lime:

• Heating limestone: CaCO₃ → CaO + CO₂

What is obtained from sea water and rock salt?

Sea water and rock salt supply sodium chloride (NaCl) and sodium bromide (NaBr).

• Sodium chloride (NaCl): occurs as rock salt in underground deposits and is dissolved in sea water.
• Importance of NaCl: it is the major starting material for many chemical industries.
• Sodium bromide (NaBr): sea water is its source, and bromine is made from it on a large scale.

What are the products of the electrolysis of NaCl?

Electrolysis of concentrated sodium chloride solution (brine) gives chlorine, sodium hydroxide and hydrogen.

What are the uses of sodium trioxocarbonate (iv) (Na₂CO₃)?

• Glass industry: a source of material for making glass.
• Detergents: used in their manufacture.
• Water softening: used by public water works to soften water.

What are the uses of chlorohydrocarbons?

• Synthetic rubber: chlorohydrocarbons are versatile raw materials for it.
• Paint removers: used as solvents.
• Refrigerants: used in cooling systems.
• Insecticides: used in several types.
• Industrial cleaning products: used in their manufacture.

What are the sources and uses of sulphur?

Sulphur is obtained as native sulphur from underground and from sulphur-containing minerals.

What are the sources of sulphur?

What is the Frasch process?

The Frasch process is the method of getting native sulphur out of underground deposits.

1. Superheated water is pumped down into the sulphur deposit.
2. The sulphur melts.
3. Compressed air forces the molten sulphur up to the surface.

What compounds and products are made from sulphur?

• Sulphur compounds: SO₂, H₂SO₃ and H₂SO₄ are produced in chemical industries.
• Fertiliser: (NH₄)₂SO₄ is made from sulphuric acid and ammonia.
• Other products: paints, dyes, explosives, synthetic fibres and accumulators.

What are metallic mineral ores used for?

A metallic mineral ore is a rock that contains enough metal compound to be worth mining.

• Use: metals are extracted from ores, for example iron from haematite and aluminium from bauxite.
• Tin: extracted from cassiterite.

What is obtained from coal?

Heating coal gives three raw materials: coke, coal gas and coal tar.

• Coke: made by heating coal, used as fuel and to reduce ores.
• Coal gas: a fuel gas from heating coal.
• Coal tar: a source of organic chemicals such as benzene and phenol.

What is obtained from natural gas and petroleum?

Natural gas and petroleum are the major raw materials for fuels and petrochemicals.

• Importance: petroleum is a major raw material for petrochemicals.
• Fuels: petrol, diesel and kerosene are petroleum products.

What are the main petrochemicals?

Petrochemicals are chemicals made from petroleum and natural gas.

What products are made from petrochemicals?

• Fertilisers: used in agriculture.
• Plastics: used for containers, pipes and household items.
• Synthetic fibres: used for clothing and fabrics.

Evaluation

1. Define a chemical industry.
2. List the seven important raw materials used in the chemical industry.
3. State two uses of NH₃.
4. Name two products obtained from the electrolysis of NaCl and state one use of each.
5. Name three sources of sulphur for industry.

Assignment

1. State three uses of calcium trioxocarbonate (iv) in the chemical industry, then list five petrochemicals obtained from petroleum.