Question

(a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
(b) name the products formed when ethanol burns in air. List two forms of energy that are liberated on burning ethanol.
(c). Why is the reaction between methane ad chlorine considered to be a substitution reaction?

Answer 1

(a) Pass the vapours of given samples of the hydrocarbons into bromine water taken in two separate test tubes. The sample which discharge the colour of brominie water is that of unsaturated hydrocarbon while the one which does not discharge the colour of bromine water, represents saturated hydrocarbon.
(b) On burning ethanol in excess of air, product is a mixture of carbon dioxide and water vapours. both heat and light are evolved in the combustion reaction.
`C_(2)H_(5)OH(l)+underset((Air))(3O_(2)(g))to2CO_(2)(g)+3H_(2)O(g)+heat+light`
(c) When methane is reacted with chlorine in the presence of sun light, tetrachloromethane is formed as the product. it is considered as substitution reaction because all the four hydrogen atoms attached to carbon atom are replaced by chlorine atoms.
`underset("Methane")(CH_(4)(g))+4Cl_(2)(g)tounderset("Tetrachloromethane")(C Cl_(4)(g))+4HCl(g)`