Uses of common elements and compounds

This is a list of commonly asked uses of substances in O level Chemistry and Combined Science exams.

Uses of oxygen

1. Medical purposes – In hospitals, oxygen is given to some people who are injured or ill with disease that damage the lungs and stop them from absorbing oxygen properly from the air.
2. Underwater breathing – Sea divers carry an oxygen tank for breathing under water. The oxygen is usually mixed with helium to reduce the effects of bends.
3. High altitude breathing – mountaineers and airmen carry oxygen for breathing at high altitudes because at high altitudes there is not enough oxygen in the atmosphere.
4. Metal cutting and welding – a mixture of acetylene and oxygen burns with a temperature of about 3000°C. The oxyacetylene flame is used to cut metals and also also to weld metals together.
5. Steel production – Oxygen is used to convert pig iron into steel. Oxygen at high pressure is blown into the molten pig iron where it oxidises impurities such as carbon, sulphur and phosphorus into oxides which escape as gases.
6. Rocket fuel oxidant – Liquid oxygen is used in some space rockets to burn fuels like kerosene and liquid hydrogen.

Uses of nitrogen

1. Haber process – Nitrogen is combined with hydrogen to produce ammonia in the haber process.
2. Providing inert environment – Petrol and oil tanks are filled with nitrogen as they runout to reduce the risk of explosions.
3. Refrigerant – Liquid nitrogen is used to freeze perishables that have high moisture content such as fruits, sea food and meat.

Uses of hydrogen

1. Fuel – Hydrogen is most efficient and cleanest gaseous fuel known. It burns in oxygen to produce water and tremendous amount of heat energy. That is why it is used and rocket fuel.
2. Welding metals – The oxyhydrogen flame burns at about 200°C and can melt most metals.
3. Manufacture of margarine – Vegetable and animal oils are liquids at room temperature. They combined with hydrogen under in the presence of a nickel or palladium catalyst to form a solid fat such as margarine.
4. Weather balloons – hydrogen is the lightest known gas. It is used to fill weather balloons because its lighter than air.
5. Haber process – Nitrogen is combined with hydrogen to produce ammonia in the haber process.

Uses of carbon dioxide

1. Fire extinguishers – Because carbon dioxide does not burn, is denser than air and doesn’t support combustion, it is used to extinguish petrol and oil fires. Petrol and oil cannot be extinguished by water because they float on water and still burn.
2. Carbonated drinks – Carbon dioxide is dissolved under pressure in fizzy drinks to give the drinks a sharp pleasant taste.
3. Refrigeration – When heated, solid carbon dioxide sublimes, i.e. it changes directly from solid to gas. It is therefore used as “dry ice” and it doesn’t leave residue when it evaporates.
4. Cloud seeding– Pieces of solid carbon dioxide are sometimes dropped into clouds to cool them enough to form rain.

Uses of ammonia

1. Manufacture of nitric acid
2. Manufacture of fertilisers – such as ammonium sulphate and ammonium nitrate.
3. Smelling salts – It is used to make smelling salts (ammonium carbonate) that act on the heart and prevents fainting and dizziness.

Uses of nitric acid

1. Manufacture of fertilisers – such as potassium nitrate, calcium nitrate, ammonium nitrate.
2. Manufacture of explosives – such as trinitrotoluene (T.N.T), trinitrocellulose and trinitroglycerine.
3. Manufacture of dyes

Uses of sulphur

1. Vulcanisation of rubber – Rubber is a soft, sticky substance that can be made hard and strong by heating it with sulphur.
2. Gun powder – gun powder is made from sulphur, potassium nitrate and charcoal.
3. Medical uses – it used to make ointments, tablets and drugs.
4. Agriculture – it is used as an insecticide and fungicide for fruit trees.
5. Contact process – it is first oxidised to sulphur dioxide, which then oxidised to sulphur trioxide in the contact process. Sulphur trioxide is then converted to sulphuric acid.

Uses of sulphur dioxide

1. Contact process – it is oxidised to sulphur trioxide in the contact process. Sulphur trioxide is then converted to sulphuric acid.
2. Bleaching – it is used in bleaching materials such as wool, straw and sponges which would be damaged by chlorine.
3. Paper making – it is used to manufacture calcium hydrogensulphite which is used to whiten wood pulp in paper making.
4. Fumigation – it is used to kill germs, termites and white ants in houses, clothing and grain.
5. Food preservation – it is used as a preservative for foodstuffs such as orange juices because it reacts with oxygen and prevents oxidation of the foodstuffs.

Uses of chlorine

1. Bleaching – it is used to bleach paper.
2. Germicide – it kills cholera, typhoid, and other pathogens in drinking water.
3. Disinfectant
4. Manufacture of chloroform – chloroform is an anaethestic.
5. Manufacture of insecticides – such as D.D.T. and Gammexane.
6. Manufacture of plastics – such as P.V.C. (Polyvinylchloride).

Uses of carbon

1. Cutting and drilling – In the form of diamond, carbon is used to cut glass, pottery and to drill rocks because diamond is the hardest known substance.
2. Pencil leads – In the form of graphite it is mixed with clay and used to produce pencil leads.
3. As a lubricant – In graphite form it is used a lubricant for dynamos and electric motors.
4. Electrodes – Graphite is used to make electrodes because it is inert and it conducts electricity.
5. In gas masks – In charcoal form, it is used in gas masks because it absorbs poison gas.
6. Whitening of sugar – Animal charcoal is used to remove the brown substances in sugar and whiten it.

Uses of hydrogen peroxide

1. Antiseptic – Hydrogen is used in mouth washes, and for cleaning wounds because it kills germs.
2. Bleaching delicate materials – It is used to bleach delicate materials such as hair, silk, teeth, which damaged by bleaching with chlorine and sulphur dioxide.
3. In rocket engines – It is used to produce oxygen for rocket engines in outer space.
4. In submarines– It is used to provide oxygen for the combustion of diesel in submerged submarine engines.

Uses of magnesium

1. Photographic flash – photographic flash powders are made by mixing magnesium with an oxidising agent.
2. Incendiary bombs – contain magnesium.
3. Aircraft industry– magnesium is alloyed with copper, aluminium and other metals to produce Duralumin, a light alloy used in aircraft industry.

Uses of aluminium

1. Aircraft industry– aluminium is alloyed with copper, magnesium and other metals to produce Duralumin, a light alloy used in aircraft industry.
2. Cooking utensils – cooking pots and pans are made with aluminium because it is a good conductor of heat and relatively inert.
3. Overhead electrical cables – they are made of aluminium because it is a good conductor of electricity and is also light.
4. Foil – it is so malleable that it can be made into thin sheets (aluminium foil) for wrapping chocolate, cigarettes. etc.

Uses of zinc

1. Galvanising iron – because it stops iron from rusting.
2. Dry cell cathode – the cathode of a dry is made of zinc.
3. Making brass – brass is an alloy of copper and zinc.

Uses of copper

1. Cooking pot and pans – making cooking utensils because it is a good conductor of heat and resistant to corrosion.
2. Making brass – brass is an alloy of copper and zinc.
3. Making bronze – bronze is an alloy of copper and tin.
4. Making electrical cables – because it is a good electrical conductor.