a. Crude oil is a mixture of hydrocarbons which belong to the homologous series called the alkanes. This mixture can be separated into fractions by the process of fractional distillation. Some of the fractions obtained are used as fuels. Some of the other fractions are subjected to catalytic cracking in order to make alkenes. Explain the meaning of the terms in italics.

b. Alkanes can be converted into substances which are used as solvents. To do this the alkane is reacted with a halogen, such as chlorine, in the presence of ultraviolet light.

(i) Write a word and balanced chemical equation for the reaction between methane and chlorine.

(ii) Name the type of reaction taking place.

(iii) Highly reactive chlorine atoms are produced in the presence of ultraviolet light. When atoms are produced in this way, what are they called?

(iv) Write a balanced chemical equation for the reaction which takes place between CHF₃ and Cl₂ to produce a chlorofluorocarbon (CFC).

(v) Why are CFCs such a problem?