basic chemistry notes (CARBON AND ITS COMPOUNDS)
basic chemistry notes part wise —
FUELS (basic chemistry notes)
- These contain carbon and, during combustion, from mainly carbon dioxide and carbon monoxide with a large amount of heat.
- Examples of solid fuels are wood, coal, coke and paraffin wax.
- These are basically mixtures or several hydrocarbons. During combustion, they form carbon dioxide and water.
- Liquid fuels are obtained as different fractions during the distillation of petroleum.
- Examples of liquid fuels are kerosene oil, petrol, diesel oil and alcohol.
- Gaseous fuels do not leave ash on burning and have the high content of heat.
- The main gaseous fuels are liquefied petroleum gas (LPG, mainly a mixture of propane and butane and used in homes for cooking, water gas (CO + H2), producer gas (CO + N2), coal gas (mixture of hydrogen, methane ethylene, carbon monoxide, nitrogen, oxygen and carbon dioxide) and natural gas (mixture of methane, ethane, propane and butane with traces of higher hydrocarbons obtained from oil well, above petroleum).
PETROLEUM AND NATURAL GAS
- Natural gas contains about 80% methane and 10% ethane, the remaining 10% being a mixture of higher gaseous hydrocarbons.
- Compressed Natural Gas (CNG) is natural gas filled in cylinders under high pressure.
- The quality of petrol for use in car engines is denoted by their anti-knock properties.
- To increase octane number, tetraethyl lead (TEL) is added to petrol.
HEAVY WATER (basic chemistry notes)
Chemically heavy water is deuterium oxide.
Heavy water is used in nuclear reactors as a moderator because it slows the fast-moving neutrons.
Hard and Soft Water
- Water which produces lather with soap solution readily is called soft water.
- Water which does not produce lather with soap solution readily is called hard water.
- The hardness of water is due to the presence of the bicarbonates, chlorides and sulphates of calcium and magnesium.
- A temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium.
- Permanent hardness of water is due to the presence of bicarbonates of calcium and magnesium.
- Ordinary glass is the solid mixture of silica, sodium silicate and calcium silicate.
- Soft glass is soda-lime silicate glass. It melts at low temperature. It is used in the manufacturing of bottles, test tubes etc.
- Hard glass is potash lime silicate and melts at a high temperature in comparison to soft glass and is used in the manufacturing of flask etc.
- Flint glass is a lead potash silicate and is used in the manufacturing of prism and lens optical instruments.
- Pyrex glass is a mixture of sodium aluminium borosilicates. It is used in manufacturing in the laboratory because it does not5 melt at very high temperature.
- Safety glass is prepared by placing a layer of transparent plastic glass between two layers of glass by means of a suitable adhesive. It is used in making windscreen of automobiles, aeroplanes, trains etc.
- The approximate composition of Portland cement is :
- Calcium Oxide → 62%
- Silica → 22%
- Alumina → 5%
- Magnesia → 5%
- Ferric Oxide → 5%
- A small amount of gypsum is added to slow down the setting of cement.
- Cement containing an excess amount of lime cracks during setting while cement containing less amount of lime is weak in strength.
- Cement containing no iron is white but hard to burn.
POLYMERS AND PLASTICS
- A polymer is a large molecule, built up from many hundreds of thousands of small unit called monomeric units or monomers.
- The process of formation of polymers from monomers is called polymerization.
- Plastics are cross-linked polymers and very tough.
- Some examples of plastics are celluloid, Bakelite and Vinyl Plastics.
- Natural and Synthetic rubbers are examples of polymers.
- Natural rubber is an isomer of isoprene.
- When the natural rubber is heated along with sulphur called The resulting rubber is elastic, hard and strong.
- Synthetic rubber is made by polymerization of chloroprene, styrene and butadiene mixtures and isobutylene.
- The soap is sodium salts of higher fatty acids. They form an insoluble precipitate in hard water. This precipitate consists of salts of calcium and magnesium of higher fatty acids. No lather or emulsion is formed and washing is not possible.
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