Reactions of alkanes and free radical substitutionEdexcel International A Level Chemistry: Mind map

Exam questions on Reactions of alkanes and free radical substitution

1. A student mixes methane and chlorine gases in a flask and exposes the flask to ultraviolet light. A reaction occurs and misty fumes of hydrogen chloride form.
   Write the equation for the initiation step, and name the type of bond fission involved.2 marks
2. A chemist reacts ethane with bromine under ultraviolet light, hoping to make bromoethane. The product mixture contains bromoethane, some dibromoethanes and a small amount of butane.
   Write the equations for the two propagation steps that form bromoethane from ethane.2 marks
3. Methane reacts with an excess of chlorine in ultraviolet light, forming chloromethane, CH₃Cl, together with further substituted products. Relative atomic masses: H = 1.0, C = 12.0, Cl = 35.5.
   Write the two propagation steps that convert chloromethane into dichloromethane, and explain why the reaction gives a mixture of chlorinated products.3 marks