Chapter 1 Practice Paper: Redox Reactions — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   In the reaction Fe₂O₃ + 3CO → 2Fe + 3CO₂, the reducing agent is

   1. AFe₂O₃
   2. BCO
   3. CFe
   4. DCO₂
   ( )
2. 2

   Which change is oxidation?

   1. ACu²⁺ → Cu
   2. BCl₂ → 2Cl⁻
   3. CZn → Zn²⁺
   4. DI₂ + 2e⁻ → 2I⁻
   ( )
3. 3

   When aqueous potassium iodide is mixed with solution X, the mixture turns red-brown. Solution X must

   1. Ais a reducing agent
   2. Bcontains iodine already
   3. Cis an oxidising agent
   4. Dis neutral
   ( )
4. 4

   In N₂O₅, the oxidation number of each nitrogen is

   1. A+5
   2. B+3
   3. C−5
   4. D+2
   ( )
5. 5

   In the displacement reaction Mg + FeSO₄ → MgSO₄ + Fe, the species reduced is

   1. AMg
   2. BFe²⁺
   3. CSO₄²⁻
   4. DMg²⁺
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Show all necessary working. Give numerical answers to 3 significant figures where appropriate, with units.

1. 1

   Hydrogen gas reduces hot copper(II) oxide: CuO + H₂ → Cu + H₂O.

   1. (a)

      State which substance is oxidised and which is reduced, in terms of oxygen.

      [2]
   2. (b)

      Name the oxidising agent and explain why it deserves that name.

      [2]
   3. (c)

      State the colour change seen as the reaction proceeds.

      [1]
2. 2

   Chlorine water is added to aqueous potassium iodide: Cl₂ + 2KI → 2KCl + I₂.

   1. (a)

      Write the two ionic half-equations for this reaction.

      [2]
   2. (b)

      Identify the oxidising agent and state the observation that supports iodine being formed.

      [2]
   3. (c)

      State the result of adding starch to the brown mixture.

      [1]
3. 3

   A student tests two colourless solutions, P and Q. Solution P decolourises acidified potassium manganate(VII). Solution Q turns aqueous potassium iodide red-brown.

   1. (a)

      State what the manganate result proves about P.

      [2]
   2. (b)

      State the reagent used in the test on Q and the species responsible for the red-brown colour.

      [2]
   3. (c)

      Classify Q and justify the classification.

      [2]
4. 4

   Consider the reaction: 2AgNO₃ + Cu → Cu(NO₃)₂ + 2Ag. Copper wire is dipped into silver nitrate solution and silver crystals grow on the wire.

   1. (a)

      Explain, in terms of electrons, why this reaction is redox.

      [2]
   2. (b)

      Name the reducing agent and state the change in its oxidation state.

      [2]