WJEC A Level Chemistry
WJEC A Level Chemistry 3.2 Redox Reactions Exam Questions
Free WJEC A Level Chemistry exam questions on 3.2 Redox Reactions, with mark schemes. Covers redox titrations with manganate(VII) and thiosulfate, and calculations.
3.2 Redox Reactions exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
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WJEC A Level Chemistry Flashcards (Anki & Quizlet)
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Use them on Anki or Quizlet, then test yourself with the questions on this page.
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About WJEC A Level Chemistry 3.2 Redox Reactions
This topic applies redox to quantitative analysis. Titration calculations are common.
What you need to know
- Manganate(VII) titrations MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O; self-indicating from colourless to pale pink.
- Iodine-thiosulfate titrations I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻ with starch indicator near the end point.
- Calculations Using mole ratios from combined half-equations.
- Applications Determining iron content or the concentration of oxidising agents.
Common mistakes in 3.2 Redox Reactions
- Using the wrong mole ratio between MnO₄⁻ and Fe²⁺ (1:5).
- Adding starch too early.
- Forgetting to acidify with sulfuric acid.
Try three 3.2 Redox Reactions exam-style questions
1. State the mole ratio of MnO₄⁻ to Fe²⁺. (1 mark)
Show the mark scheme answer
1 : 5.
2. Explain why starch is added near the end point. (1 mark)
Show the mark scheme answer
Adding it too early forms a complex with lots of iodine that is slow to react.
3. Explain why manganate(VII) titrations need no indicator. (1 mark)
Show the mark scheme answer
MnO₄⁻ is purple and turns colourless, so the first permanent pink shows the end point.
3.2 Redox Reactions FAQs
What does Redox Reactions cover?
Redox titrations and their calculations.
Which practical links here?
Redox titration, for example determining iron in a tablet.
Why use sulfuric acid?
It provides H⁺ without being oxidised, unlike hydrochloric acid.
Revise this topic with flashcards: WJEC A Level Chemistry Flashcards, with mark scheme answers for Anki and Quizlet.
