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CAIE A-Level Chemistry AS 14.1.2 Describe Questions

Practise balancing complete and incomplete alkane combustion equations and describing chlorine or bromine free-radical substitution under ultraviolet light in CAIE 9701 questions.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • write balanced equations for complete combustion of an alkane to carbon dioxide and water, and for incomplete combustion to carbon monoxide or carbon
  • state chlorine or bromine with ultraviolet light for free-radical substitution of an alkane and write the overall substitution equation
  • recognise further substitution and product mixtures when excess halogen reacts with ethane or methane rather than assuming one product

CAIE A-Level Chemistry AS 14.1.2 Describe Questions question 1

[Maximum number: 2]

Allyl chloride is an important chemical used in the manufacture of plastics, pharmaceuticals and pesticides.

allyl chloride

allyl chloride

Question (a)

(a)

Allyl chloride can be produced by many different methods. The most common method is chlorination of propene which proceeds via a free-radical substitution mechanism.

Figure for Question (a) — CAIE A-Level Chemistry AS
[ 2 ]

Question (i)

(i)

The initiation step in this reaction is the formation of chlorine radicals ( Cl∙\mathrm{C} l^{\bullet} ) from Cl2\mathrm{Cl}_{2} molecules.

State the conditions required to initiate this reaction.

[ 1 ]

Question (ii)

(ii)

Explain why the free-radical substitution reaction gives a low yield of allyl chloride.

[ 1 ]
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