3 c) alkenes

Question 1

3.6 recall that alkenes have the general formula CnH2n

Answer 1

Alkenes have the general formula CnH2n

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Question 2

3.7 draw displayed formulae for alkenes with up to four carbon atoms in a molecule, and name the straight-chain isomers (knowledge of cis- and trans- isomers is not required)

Answer 2

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Question 3

3.8 describe the addition reaction of alkenes with bromine, including the decolourising of bromine water as a test for alkenes.

Answer 3

An alkene will make its double bond into a single bond, to bond to two bromines. Bromine is added to the molecule. The product made is colourless. When alkenes are put in bromine water it turns from brown to colourless.

For example:

C2H4(g) + Br2 (aq) ==> C2H4Br2 (aq)