Chapter 12 Practice Paper: Rates of reaction — question paper

Section A: Multiple-choice questions[10 marks]

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

1. 1

   A reaction makes 30 cm³ of gas in 20 s. The mean rate is

   1. A1.5 cm³/s
   2. B0.67 cm³/s
   3. C600 cm³/s
   4. D10 cm³/s
   ( )
2. 2

   For a collision to be successful it must have energy at least equal to the

   1. Abond energy of the product
   2. Broom temperature
   3. Cactivation energy
   4. Dgas volume
   ( )
3. 3

   Increasing concentration increases the rate by making collisions

   1. Amore energetic
   2. Bmore frequent
   3. Clarger
   4. Dcolder
   ( )
4. 4

   Which change slows a reaction?

   1. AGrinding the solid
   2. BAdding a catalyst
   3. CRaising the pressure of gases
   4. DCooling the mixture
   ( )
5. 5

   A catalyst is best described as a substance that

   1. Aspeeds a reaction without being consumed, by lowering activation energy
   2. Bis consumed while speeding a reaction
   3. Cslows unwanted reactions
   4. Draises the temperature
   ( )
6. 6

   A volume–time graph becomes horizontal when

   1. Athe catalyst is used up
   2. Bthe reaction has finished
   3. Cthe gas dissolves
   4. Dthe syringe is full
   ( )
7. 7

   The rate at a single moment on a curve is found from

   1. Athe final volume
   2. Bthe area under the curve
   3. Cthe gradient of a tangent at that point
   4. Dthe curve’s length
   ( )
8. 8

   In the disappearing-cross experiment, a faster rate is shown by

   1. Aa longer time
   2. Ba darker cross
   3. Ca larger flask
   4. Da shorter time for the cross to vanish
   ( )
9. 9

   Powders react faster than lumps because powders have

   1. Agreater surface area exposed to collisions
   2. Bmore energetic particles
   3. Clower melting points
   4. Dfewer bonds
   ( )
10. 10

    Two curves use equal reactant amounts at different temperatures. Both end

    1. Aat different volumes
    2. Bat the same volume, the hotter one sooner
    3. Cat the same time
    4. Dat zero
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 11

   Marble chips and hydrochloric acid produce CO₂, measured by mass loss on a balance.

   1. (a)

      Explain why the balance reading falls during the reaction.

      [2]
   2. (b)

      The mass falls by 0.88 g in the first 40 s. Calculate the mean rate in g/s.

      [1]
   3. (c)

      State one advantage of the gas syringe method over mass loss for this reaction.

      [2]
2. 12

   Explain, using collision theory, the effect of each change on the rate of magnesium reacting with hydrochloric acid.

   1. (a)

      Heating the acid from 20 °C to 40 °C.

      [3]
   2. (b)

      Using 2.0 mol/dm³ acid instead of 1.0 mol/dm³ at the same temperature.

      [3]
   3. (c)

      Replacing the magnesium ribbon with an equal mass of powder.

      [3]
3. 13

   A student collects hydrogen from magnesium and acid every 20 seconds.

   Gas volumes

   Time / s	Volume / cm³
   0	0
   20	34
   40	52
   60	60
   80	62
   100	62

   1. (a)

      Calculate the mean rate over the first 20 s.

      [1]
   2. (b)

      Explain why the rate falls during the experiment.

      [2]
   3. (c)

      When is the reaction complete? Explain.

      [1]
   4. (d)

      A tangent at 40 s has a gradient of 0.9 cm³/s. State what this represents.

      [2]