Exam-style Questions: Rates of Reaction

 

  1. An experiment was carried out to look at the reaction between magnesium and hydrochloric acid.

    The word equation for this reaction is:

    Magnesium + Hydrochloric Acid → Magnesium Chloride+Hydrogen

    a) What would you see when this reaction is taking place?

    (1 mark)

    b) Give three ways in which the rate of reaction could be increased.

    (3 marks)

    (Marks available: 4)

    Answer

     

    Answer outline and marking scheme for question: 1

    a) Bubbles of gas/hydrogen/effervescence/metals fizzes.

    (1 mark)

    b) Any three from:

    • Increase the temperature/heat mixture.
    • Increase concentration of acid (not add more acid).
    • Add more magnesium.
    • Cut up/powder the magnesium.
    • Add a suitable catalyst.

     

    (maximum, 3 marks)

    (Total = 4 marks)

  2. The following graphs were obtained in an experiment to look at the reaction between nickel carbonate and hydrochloric acid:

    Exam-style Questions

    a) Write a word equation for the reaction between nickel carbonate and hydrochloric acid.

    (1 mark)

    b) Which of the graphs shows the reaction that had the most concentrated hydrochloric acid?

    Explain your answer.

    (2 marks)

    (Marks available: 3)

    Answer

     

    Answer outline and marking scheme for question: 2

    a)

    Nickel carbonate + hydrochloric acid → nickel chloride + carbon dioxide + water

    (1 mark)

    b) A,

    (1 mark)

    because the graph is the steepest showing carbon dioxide is made the fastest.

    (1 mark)

    (Total = 3 marks)

  3. Hydrogen peroxide decomposes at room temperature to give oxygen and water:

    Hydrogen peroxide → oxygen + water

    a) Which piece of apparatus could be used to measure the rate of this reaction?

    (1 mark)

    b) What effect would adding manganese (IV) oxide have on the rate of this reaction?

    (1 mark)

    c) What name do we give to chemicals like manganese (IV) oxide?

    (1 mark)

    (Marks available: 3)

    Answer

     

    Answer outline and marking scheme for question: 3

    a) Gas syringe/inverted measuring cylinder full of water/balance.

    (1 mark)

    b) Rate would increase.

    (1 mark)

    c) Catalysts.

    (1 mark)

    (Total = 3 marks)

  4. Most of the chemical reactions that take place in living organisms involve enzymes.

    a) Explain the term 'enzyme'.

    (1 mark)

    b) Catalase is an enzyme that is found in liver. It can cause a change in the decomposition of hydrogen peroxide.

    What effect would you expect if a piece of liver was placed in hydrogen peroxide solution?

    (1 mark)

    c) If manganese (IV) oxide is added to hydrogen peroxide the rate of reaction increases. If the mixture is heated to 80oC the reaction is vigorous. If the same is done with a piece of liver the reaction rate is less at 80oC.

    Explain these observations.

    (2 marks)

    (Marks available: 4)

    Answer

     

    Answer outline and marking scheme for question: 4

    a) A biological catalyst.

    (1 mark)

    b) Rate would increase/oxygen is made faster.

    (1 mark)

    c) Manganese (IV) oxide is a catalyst. When mixture is heated rate is increased due to usual effect of increased temperature on rate.

    (1 mark)

    Catalase is denatured/broken down at higher temperatures (60oC+) so heating the solution destroys the catalyst and so its effect is lost - rate lowered.

    (1 mark)

    (Total = 4 marks)