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IB Chemistry SL 3.3 Electron Sharing Reactions Radicals Questions

Use IB Chemistry SL questions to identify radicals, explain homolytic fission and write initiation, propagation and termination steps.

Syllabus
First assessment 2025
Course
Chemistry SL
Level
SL

Exam points

  • Define a free radical as a neutral species with an unpaired electron, interpret dot notation and distinguish radicals from ions or closed-shell molecules.
  • Explain homolytic fission as equal electron splitting of a covalent bond, using single-barbed arrows and UV-light or heat initiation.
  • Write propagation steps for alkane halogenation, showing radical consumption and regeneration of the chain carrier.
  • Write termination by combining radicals and explain why radical substitution produces a mixture of products.

Covered syllabus points

3.3.1—Radicals3.3.2—Homolytic fission3.3.3—Radical substitution

Question 1

[Maximum number: 1]

Antioxidants are a type of food additive.

Antioxidants such as BHT and 3-BHA prevent the unwanted reactions of free radicals. State what a free radical is.

Question 2

[Maximum number: 2]

Alkenes, such as A (shown below), are important intermediates in the petrochemical industry because they undergo addition reactions to produce a wide variety of products, such as the conversion shown below.

Figure for Question 2 — IB Chemistry SL

Question (a)

(a)

Another way to make B is the reaction shown below.

Figure for Question (a) — IB Chemistry SL
[ 2 ]

Question (i)

(i)

State the conditions required for this reaction to occur.

[ 1 ]

Question (ii)

(ii)

Outline why it would give a poor yield of the desired product.

[ 1 ]

Question 3

[Maximum number: 1]

Chlorine undergoes many reactions.

State the type of reaction occurring when ethane reacts with chlorine to produce chloroethane.

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