Topic 6 Practice Paper: Chemical reactions — question paper

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1. 1

   Which of the following is a chemical change rather than a physical change?

   1. ABoiling ethanol to form a vapour
   2. BMelting butter in a warm room
   3. CHeating copper carbonate to give copper oxide and carbon dioxide
   4. DDissolving salt in water
   ( )
2. 2

   A reaction is carried out once with a catalyst and once without it. What effect does the catalyst have?

   1. AIt lowers the activation energy so more collisions are successful
   2. BIt increases the yield of product at equilibrium
   3. CIt raises the energy of the products formed
   4. DIt is consumed gradually as the reaction proceeds
   ( )
3. 3

   When the temperature of a reaction mixture is raised, what happens to the particles?

   1. AThey become smaller and lighter
   2. BThey stop colliding with one another
   3. CThey collide less often in total
   4. DThey move faster, so more collisions have the activation energy
   ( )
4. 4

   Which pair of changes would both increase the rate of reaction between limestone chips and dilute hydrochloric acid?

   1. AUsing larger chips and cooling the acid
   2. BUsing powdered limestone and warming the acid
   3. CDiluting the acid and using larger chips
   4. DCooling the mixture and diluting the acid
   ( )
5. 5

   Which of the following is a reversible reaction?

   1. AThe complete combustion of methane in oxygen
   2. BThe neutralisation of hydrochloric acid by sodium hydroxide
   3. CThe heating of ammonium chloride to give ammonia and hydrogen chloride, which re-form on cooling
   4. DThe reaction of magnesium with oxygen to form magnesium oxide
   ( )
6. 6

   For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the forward reaction is exothermic. Which change shifts the position of equilibrium to the right?

   1. AIncreasing the pressure
   2. BDecreasing the pressure
   3. CRaising the temperature
   4. DAdding a catalyst
   ( )
7. 7

   Which statement about a catalyst is correct?

   1. AIt is used up during the reaction
   2. BIt changes the position of equilibrium
   3. CIt increases the energy released by the reaction
   4. DIt speeds up both the forward and the reverse reactions
   ( )
8. 8

   In the reaction Fe₂O₃ + 3CO → 2Fe + 3CO₂, which substance is oxidised?

   1. AFe₂O₃
   2. BCO
   3. CFe
   4. DCO₂
   ( )
9. 9

   Which change is an oxidation in terms of electrons?

   1. AGain of electrons
   2. BLoss of oxygen
   3. CGain of hydrogen
   4. DLoss of electrons
   ( )
10. 10

    Acidified potassium manganate(VII) is added to a solution and its purple colour disappears. What does this show about the solution?

    1. AIt is a strong acid
    2. BIt contains a reducing agent
    3. CIt contains an oxidising agent
    4. DIt contains a catalyst
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 11

   A student is given four changes: (i) ice melting, (ii) a magnesium ribbon burning, (iii) sugar dissolving in water, (iv) an iron nail rusting.

   1. (a)

      State which two changes are chemical changes.

      [1]
   2. (b)

      Give two observations that would show a chemical change is taking place during (ii).

      [2]
   3. (c)

      Explain why change (i) is a physical change.

      [1]
2. 12

   Marble chips (calcium carbonate) react with dilute hydrochloric acid to give carbon dioxide. A student follows the reaction by measuring the loss in mass.

   1. (a)

      Name the gas produced and give a test for it.

      [2]
   2. (b)

      The student repeats the experiment using the same mass of powdered marble instead of chips. State and explain the effect on the rate.

      [2]
   3. (c)

      Explain how warming the acid changes the rate, in terms of particles (Supplement).

      [2]
3. 13

   Ammonia is made industrially by the Haber process.

   1. (a)

      Write the symbol equation for the reaction, including the equilibrium sign.

      [1]
   2. (b)

      State the source of the hydrogen used.

      [1]
   3. (c)

      The forward reaction is exothermic. Explain how increasing the temperature affects the rate and the yield of ammonia.

      [3]
4. 14

   A redox reaction takes place when iron(III) oxide reacts with carbon monoxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂.

   1. (a)

      State the oxidation number of iron in Fe₂O₃.

      [1]
   2. (b)

      Explain, in terms of oxidation number, why this is a redox reaction.

      [2]
   3. (c)

      Identify the reducing agent and explain your choice.

      [2]