(a) Covalent compounds of carbon and hydrogen are called hydrocarbons.
(b) Saturated hydrocarbons have single covalent bonds between carbon atoms whereas unsat-urated hydrocarbons have double or triple covalent bonds between carbon atoms.
(c) Because soap reacts with calcium and magnesium salts present in hard water to form an insoluble scum and no lather is produced.
(d) It is because of the structure of soap molecule. The hydrophilic end of soap dissolves in water while hydrophobic end dissolves in hydrocarbon.
(e) Hydrolysis of an ester by either alkali or an acid to give alcohol and carboxylic acid is called saponification.