⚡ Redox Masterclass: Past Papers
Cambridge IGCSE Chemistry 0620 · Oxidation, Reduction & Electron Transfer
Section A: Cl₂ + 2KI → 2KCl + I₂
5 questions · 8 marks
Identify the substance that is oxidised in this reaction.
Identify the oxidising agent in this reaction.
Explain why Cl₂ is the oxidising agent using electron transfer.
Write the ionic half-equation for the oxidation of iodide ions.
Use oxidation numbers to show that chlorine is reduced in this reaction.
Section B: Fe₂O₃ + 3CO → 2Fe + 3CO₂
5 questions · 11 marks
Identify the reducing agent in this reaction and explain using oxidation numbers.
Identify the substance that is reduced. Give the oxidation number change as evidence.
Write the half-equation for the reduction of Fe³⁺ to Fe.
This reaction is used in the extraction of iron in the blast furnace. Explain why CO is a suitable reducing agent for this process.
State the oxidation number of oxygen in Fe₂O₃ and in CO₂. What do you notice?
Section C: Laboratory Tests
5 questions · 15 marks
A student believes that gas X is a reducing agent. Describe a chemical test to prove this, including the expected observation if gas X IS a reducing agent.
A student suspects substance Y is an oxidising agent. Describe a test using potassium iodide (KI) solution and starch to confirm this.
A student adds iron(II) sulfate solution to acidified potassium manganate(VII). State the colour change and identify which species is oxidised.
Write the ionic half-equation for the reduction of manganate(VII) ions (MnO₄⁻) in acidic conditions. The product is Mn²⁺.
A student adds bromine water to a solution. The bromine water turns from orange to colourless. What does this tell the student about the solution? Explain in terms of electron transfer.
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