Chemical reactions of the alkenes
5 marks · HardThis question is about reactions of hexene (C6H12).
Describe what happens to the C=C double bond in an addition reaction of hexene.
State the product formed when hexene reacts with hydrogen in an addition reaction. Suggest the molecular formula of the product.
Write a chemical equation for the complete combustion of hexene.
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(a) The double bond breaks; each carbon forms a new single bond with atoms from the added molecule. · must show Breaks double bond, Forms two new single bonds
(b) Hexane; C6H14 · must show Hexane name, C6H14
(c) C6H12 + 9O2 → 6CO2 + 6H2O · must show Correct balanced equation
Common mistakes: Incorrect formula for addition product; Incorrect number of oxygen molecules
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Describes that the C=C double bond breaks.
B2 (a) · 1 mark · States that each carbon atom forms a new bond with atoms from the added molecule.
B3 (b) · 1 mark · Identifies the product as hexane.
B4 (b) · 1 mark · Molecular formula for product is C6H14.
B5 (c) · 1 mark · Gives correct balanced combustion equation: C6H12 + 9O2 → 6CO2 + 6H2O.
Worked solution
(a) During an addition reaction, the double bond in hexene breaks, and each carbon atom forms a new single bond with an atom from the added molecule.
(b) When hexene reacts with hydrogen, the product is hexane. The molecular formula is C6H14.