SC22b Reactions of Alkanes and Alkenes

Question 1

addition reaction?

Answer 1

when 2 reactants add together to make 1 product

Question 2

reaction of ethene and bromine

Answer 2

ethene + bromine → 1,2-dibromoethene

Question 3

structural formula of the reaction of ethene and bromine?

Answer 3

H H H H
C=C + Br₂ → H-C-C-H
H H Br Br

Question 4

complete combustion?

Answer 4

combustion of hydrocarbons with enough oxygen present to convert all the fuel into carbon dioxide and water

Question 5

what is the chemical test for alkenes and alkanes?

Answer 5

orange bromine water stays orange in alkanes as they have no double bonds but goes colourless in alkenes

Question 6

Bottles of two liquids, hexane and hexene, have been muddled. Explain how bromine water might be used to distinguish between them. 2 marks

Answer 6

Hexene will decolourise bromine water from orange-brown to colourless (1)​

Hexane will not decolourise bromine water, so the orange-brown colour of the bromine remains (1).​