(a) Why does carbon form compounds mainly by covalent bonding? (b) List any two reasons for carbon forming a very large number of compounds. (c) An organic acid ‘X’ is a liquid which often freezes during winter time in cold countries, has the molecular formula, C2H4O2. On warmong it with ethanol in the presence of a few drops of concentrated sulphuric acid, a compound ‘Y’ with a sweet smell is formed. (i) Identify ‘X’ and ‘Y’. (ii) Write a chemical equation for the reaction involved.
(a) Carbon has 4 electrons in its valence shell. In order to attain stability, it can neither gain 4 electrons nor lose 4 electrons as losing 4 electrons involves a lot of energy. Also, it cannot gain 4 electrons because the nucleus cannot hold on to the four extra electrons added. Hence, to complete the octet, it shares 4 electrons with other atoms. This is why carbon forms compound mainly by covalent bonding. (b) Catenation and tetravalency nature of carbon is the reason for the formation of a large number of compounds. The property of the formation of bonds with other carbon atoms to form long chains of different compounds is called catenation. Carbon has 4 electrons in its outermost orbit so it is a tetravalent compound. (c) (i) The organic acid, X, which often freezes in the winters in cold countries, is ethanoic acid. It has the molecular formula CH3COOH. Y is methyl ethanoate Its formula is CH3COOCH3. (ii) The chemical equation is given below: CH3COOH + CH3OH - CH3COOCH3 + H20
