Chemistry (NTSE/Olympiad)  

6. Carbon and Its Compound

Points to Remember (Carbon and its compounds)

♦ Carbon always forms covalent bonds.
♦ Carbon is present in all substances of animal and vegetable origin
♦ The ability of carbon to unite with an indefinite number of carbon atoms in straight, branched or cyclic chains is known as catenation.
♦ Caron and hydrogen combine together indifferent proportions to form a large number of compounds called hydrocarbons.
♦ There are two types of hydrocarbons-saturated and unsaturated
♦ Alkanes are represented by the general formula CnH2n+2.
♦ Alkenes are represented by the general formula CnH2n.
♦ Alkynes are represented by the general formula CnH2n–2.
♦ Organic compounds having the same functional group and common properties, but differing in molecular formula from the next member by one CH2 group, form a homologous series and such compounds are called homologues.
♦ Compounds with the same molecular formula but different structural formulae are known as isomers.
♦ The decomposition of alkanes on heating in the absence of oxygen is known as cracking.
♦ Methane is prepared by heating a mixture of sodium acetate and soda lime.
♦ When ethanol is heated with an excess of concentrated sulphuric acid at 160°C, ethene gas is produced.
♦ Natural gas is a mixture of gaseous hydrocarbons, mainly methane, ethane, propane and butane.
♦ Compressed Natural Gas (CNG) is used as an alternative to petrol as automobile fuel.
♦ Natural gas is a rich source of hydrogen gas which is required for the manufacture of fertilizers
♦ Liquefied Petroleum Gas (LPG) is used as a domestic fuel.
♦ Petrol is a complex mixture of hydrocarbons such as hexane, heptane and octane.
♦ Petrol is used as a motor fuel.
♦ Alcohols are organic compounds which contain hydroxyl group (–OH) bonded to a carbon atom.
♦ Alcohols are neutral to litmus.
♦ Alcohols are poor conductors of electricity.
♦ Alcohol reacts with sodium to liberate hydrogen gas.
♦ Ethanol is a constituent of beverages, like wine and beer.
♦ Ethanol is used as a hypnotic and is highly addictive.
♦ Organic compounds containing carboxyl group (–COOH) are called carboxylic acids.
♦ Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas.
♦ A dilute aqueous solution 4 – 6% of ethanoic acid is called vinegar
♦ A 99% pure solution of acetic acid is called glacial acetic acid.
♦ A soap is a sodium or potassium salt of a long-chain carboxylic acid. Sodium palmitate, sodium stearate, etc., are examples of soaps.
♦ The process of splitting fats or oils using alkalis is called saponification.
♦ Soaps do not work well with hard water, but synthetic detergents do.
♦ Soaps are biodegradable, but synthetic detergents are not.


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