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Chapter 4 Practice Paper: Rate of Reactions — question paper

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QQ/S4CH/CH4

Secondary 4 · Chemistry (G2 / G3)

Chapter 4 Practice Paper

Rate of Reactions

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Chemical equations should be balanced, with state symbols shown where the question asks for them.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is shown on its cover.

Original practice material written for the MOE Chemistry syllabus. It is not an official MOE or school examination paper. Chapter 4 (measuring rates, collision theory, rate factors, graph interpretation).

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    In which experiment would measuring the LOSS OF MASS of the apparatus over time be a sensible way to follow the rate?

    1. Azinc + dilute hydrochloric acid in an open flask
    2. Bhydrochloric acid + sodium hydroxide in a closed flask
    3. Csilver nitrate + sodium chloride in a stoppered flask
    4. Dcrystallising copper sulfate from a saturated solution
    ( )
  2. 2

    A rate curve is steep at first and flattens later. The flattening happens because

    1. Athe catalyst has been used up
    2. Bthe reactant particles have lost their charge
    3. Cthe temperature has dropped to room temperature
    4. Dthe concentration of the reactants has fallen
    ( )
  3. 3

    Which single change makes the reaction between calcium carbonate and hydrochloric acid faster WITHOUT changing the final volume of carbon dioxide (acid in excess in both cases)?

    1. Ausing half the mass of calcium carbonate
    2. Busing the same mass of calcium carbonate as powder
    3. Cdiluting the acid with an equal volume of water
    4. Dcooling the acid to 5 °C
    ( )
  4. 4

    The curve for an experiment at 35 °C is compared with one at 25 °C. The 35 °C curve

    1. Ais steeper and plateaus higher
    2. Bis shallower and plateaus lower
    3. Cis steeper and plateaus at the same height (same reactant amounts)
    4. Dcoincides exactly with the 25 °C curve
    ( )
  5. 5

    MnO₂ catalyses 2H₂O₂ → 2H₂O + O₂. After the reaction the MnO₂ is recovered dry and weighs the same. This shows the MnO₂

    1. Awas converted into water
    2. Bacted as the limiting reactant
    3. Cprovided oxygen gas itself
    4. Dspeeded the reaction without being consumed
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Include state symbols where the question asks, and balance every equation.

  1. 1

    Excess dilute hydrochloric acid is added to 1.00 g of magnesium ribbon (Mr = 24) and the hydrogen is collected in a gas syringe.

    1. (a)

      Write the equation for the reaction.

      [1]
    2. (b)

      Calculate the volume of hydrogen expected at r.t.p. (24 dm³ per mole), and state where the syringe reading plateaus.

      [3]
    3. (c)

      State and explain how the curve would differ if the same mass of magnesium powder were used.

      [2]
  2. 2

    A student investigates the reaction between sodium thiosulfate solution and dilute hydrochloric acid at three temperatures, timing how long a cross drawn under the beaker takes to disappear.

    1. (a)

      Name the product responsible for the cloudiness.

      [1]
    2. (b)

      Predict the order of the three times (fastest to slowest) for 40 °C, 30 °C and 20 °C.

      [1]
    3. (c)

      Explain, using collision theory, why the higher temperature gives a shorter time.

      [3]
  3. 3

    Two gas syringes collect the carbon dioxide from identical masses of marble in identical excess acid. Run A uses chips at 20 °C; run B uses chips at 40 °C.

    1. (a)

      Sketch-in-words both curves on the same axes.

      [2]
    2. (b)

      Explain why curve B is steeper.

      [2]
    3. (c)

      State what the common plateau height represents.

      [1]
  4. 4

    Hydrogen peroxide decomposes slowly at room temperature: 2H₂O₂ → 2H₂O + O₂. A few grams of manganese(IV) oxide powder are added and oxygen pours out.

    1. (a)

      State the role of the manganese(IV) oxide and describe a test for the gas.

      [2]
    2. (b)

      Explain why the total volume of oxygen collected is the same with and without the MnO₂.

      [2]

— End of paper —