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IB Chemistry HL 3.2.2 Half Equations Questions

Use real HL exam questions to balance half-equations, combine them into overall redox equations and identify oxidation at each electrode.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • Write and balance oxidation or reduction half-equations in acidic or neutral solution, conserving atoms, charge and electrons and including requested state symbols.
  • Combine oxidation and reduction half-equations to produce a balanced overall redox equation, using the lowest whole-number electron ratio.
  • Identify which half-equation represents oxidation or reduction and assign electrode reactions from electron loss or gain, checking the electron balance.

Learn this topic

Study 3.2.2—Half-equations conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Chemistry HL 3.2.2 Half Equations Questions question 1

[Maximum number: 4]

Bleaches in which chlorine is the active ingredient are the most common, although some environmental groups have concerns about their use.

Aqueous sodium chlorate(I), NaOCl, the most common active ingredient in chlorine based bleaches, oxidizes coloured materials to colourless products while being reduced to the chloride ion. It will also oxidize sulfur dioxide to the sulfate ion.

Deduce a balanced equation for the reaction between the chlorate(I) ion and sulfur dioxide from the appropriate half-equations.

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