How are methane and ethane prepared from methyl iodide and ethyl bromide?

What is a substitution reaction? Give the reaction of chlorine with ethane and name the product formed.

Write the names and the formula of the products formed when:

(a) methane (b) ethane

reacts with (i) chlorine (ii) bromine

Write the chemical equations.

Name the compound prepared from:

(a) Sodium propionate

(b) Methyl iodide and

(c) Ethyl bromide.

Write a balanced equation for the same.