Reactions of alkanes and free radical substitutionEdexcel International A Level Chemistry: Flashcards
What these 14 flashcards ask
- What is a free radical?
- What is homolytic fission?
- What do curly half-arrows show?
- Condition for alkane + halogen to react?
- Initiation step for chlorine
- First propagation step for methane + chlorine
- Second propagation step for methane + chlorine
- What is a termination step?
- Give two termination equations in methane + chlorine
- Why is the reaction a chain reaction?
- Why is the reaction of limited use in synthesis?
- What type of reaction is CH₄ + Cl₂ → CH₃Cl + HCl?
- Products of complete combustion of an alkane
- How can further substitution be reduced?
Exam questions on Reactions of alkanes and free radical substitution
- 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
- 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
- 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
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).