A LevelChemistryOCRExam Questions5. Physical Chemistry & Transition ElementsRates, Orders & Arrhenius

Rates, Orders & Arrhenius (OCR A Level Chemistry A): Exam Questions

Exam code: H432

4 hours33 questions

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Rates, Orders & Arrhenius

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1
1 mark

The reaction between iodine and propanone can be catalysed by sulfuric acid. The rate equation shows that this reaction is first order with respect to propanone:

Rate = k [H+] [C3H6O]

Which graph shows that the reaction is first order with respect to propanone?

Four rate-concentration lines/curves labelled A to D showing different curve shapes for selection, plotted on one chart

    Choose your answer

    2
    1 mark

    Substances W and X react in solution according to the equation.

    W + 2X → Y + 2Z

    The results of an investigation of the reaction between W and X are shown in this table.

    Experiment

    Initial [W] / mol dm–3

    Initial [X] / mol dm–3

    Initial rate / mol dm–3 s–1

    1

    0.50

    0.50

    7.0 x 10-4

    2

    0.50

    1.00

    To be calculated

    The reaction is zero order with respect to W and first order with respect to X.

    What is the initial rate of experiment 2?

    • 2.8 x 10-3 mol dm–3 s–1

    • 1.4 x 10-3 mol dm–3 s–1

    • 7.0 x 10-4 mol dm–3 s–1

    • 3.5 x 10-4 mol dm–3 s–1

    Choose your answer

    3
    1 mark

    The rate equation for the reaction between X and Y is:

    Rate = k [X] [Y]

    What are the correct units for the rate constant, k, of this rate equation?

    • mol dm-3 s-1

    • mol2 dm-6 s-1

    • dm6 mol-2 s-1

    • dm3 mol-1 s-1

    Choose your answer

    4
    1 mark

    The Arrhenius equation is shown below.

    k = Ae-Ea / RT

    Which term from the Arrhenius equation does not have the correct units?

     

    Term

    Units

    A

    Ea

    kJ K⁻¹ mol⁻¹

    B

    R

    J K-1 mol-1

    C

    T

    K

    D

    e

    No units

      Choose your answer

      5
      1 mark

      An alternative version of the Arrhenius equation is:

      ln space k space equals space fraction numerator negative E subscript straight a over denominator R end fraction space 1 over T space plus space ln space A

      Which specific term can be calculated from an Arrhenius plot, shown below, using this equation?

      Arrhenius plot showing ln k on the y-axis against 1/T on the x-axis with a straight line of negative gradient

      • Ea

      • begin mathsize 14px style 1 over T end style

      • R

      • begin mathsize 14px style 1 over R end style

      Choose your answer

      1
      1 mark

      Which concentration–time graph represents a reaction that is zero order with respect to a reactant?

      • blQswxWs_conc-time-graph-option-a
      • SfDyTwrV_conc-time-graph-option-b
      • 3Q~Rijan_conc-time-graph-option-c
      • juhr5Pl~_conc-time-graph-option-d

      Choose your answer

      2
      1 mark

      The reaction between iodine and propanone can be catalysed by sulfuric acid. The rate equation for this reaction is:

      Rate = k [H+] [C3H6O]

      Which row, describing the order of reaction with respect to each chemical involved, is correct? 

       

      Iodine

      Propanone

      Sulfuric acid

      A

      Zero

      First

      Second

      B

      First

      Zero

      First

      C

      Zero

      First

      First

      D

      Zero

      Second

      Zero

        Choose your answer

        3
        Sme Calculator
        1 mark

        An investigation into the rate of reaction between compounds A and B was performed. 

        A + B → Products 

        The results from three different experiments carried out at a constant temperature are shown:

        Expt. 

        Initial concentration of A / mol dm-3

        Initial concentration of B / mol dm-3

        Initial rate / mol dm-3 s-1

        1

        0.30

        0.50

        6.0 x 10-4

        2

        0.30

        0.25

        1.5 x 10-4

        3

        0.60

        0.25

        3.0 x 10-4

        The rate equation for this reaction is rate = k [A] [B]2

        What is the value of the rate constant, k? 

        • 2.0 × 10-3 dm6 mol-2 s-1

        • 3.2 × 10-2 dm6 mol-2 s-1

        • 8.0 × 10-3 dm6 mol-2 s-1

        • 2.7 × 10-2 dm6 mol-2 s-1

        Choose your answer

        4
        1 mark

        Which rate-concentration graph represents a reaction that is second order with respect to a reactant?

        • Graph with two axes meeting at a right angle; one arrow points up and the other right. A line with positive slope extends from origin.
        • blQswxWs_conc-time-graph-option-a
        • 3Q~Rijan_conc-time-graph-option-c
        • juhr5Pl~_conc-time-graph-option-d

        Choose your answer

        5
        Sme Calculator
        1 mark

        A graph is plotted of ln k against 1/T.

        (k = rate constant, T = temperature in K)

        The gradient has the numerical value of −45000.

        What is the activation energy, in kJ mol−1?

        • 374 kJ mol−1

        • 374 130 kJ mol−1

        • −374 kJ mol−1

        • 5.42 kJ mol−1

        Choose your answer

        6
        1 mark

        The rate constant, k, of a reaction was determined at various temperatures, T.

        A graph of ln k against 1/T was plotted.

        The gradient of the straight line of best fit was −5.50 × 103 K.

        The gas constant is R = 8.314 J mol−1 K−1.

        What is the activation energy, Ea, for this reaction?

        • −45.7 kJ mol-1

        • 45.7 kJ mol-1

        • 662 kJ mol-1

        • 45 700 kJ mol-1

        Choose your answer

        1
        Sme Calculator
        1 mark

        Using the graph, what is the value of the pre-exponential factor, A, for the decomposition of N2O5?

        2N2O5(g) → 4NO(g) + O2(g)

        Arrhenius plot for decomposition of N2O5 showing ln k against 1/T with a straight line; y-intercept at approximately 31.5

        • 3.45 s-1

        • 31.5 s-1

        • 1.04 × 105 s-1

        • 4.79 × 1013 s-1

        Choose your answer

        2
        1 mark

        Acidified propanone was added to a solution of iodine. The rate equation is:

        rate = k[CH3COCH3][H+]2

        The initial rate of reaction is 2.75 x 10-3 mol dm-3

         

        CH3COCH3

        I2

        H+

        Initial concentration (mol dm-3)

        3.32

        0.25

        0.73

        What is the value of the rate constant, k?

        • 1.55 x 10-3 mol-2 dm6 s-1

        • 1.13 x 10-3 mol-2 dm6 s-1

        • 1.55 x 10-3 mol dm3 s-1

        • 1.13 x 10-3 mol dm3 s-1

        Choose your answer

        3
        1 mark

        The Arrhenius equation can be used to calculate the activation energy of a reaction. The gas constant, R = 8.31 J K-1 mol-1.

        bold 1 over bold T K-1

        ln k

        0.00347

        -10.9

        0.00336

        -9.7

        0.00325

        -8.5

        0.00314

        -7.3

        0.00305

        -6.1

        What is the activation energy for this reaction to 3 significant figures?

        • 7.62 x 10-4 kJ mol-1

        • -7.62 x 10-4 kJ mol-1

        • 90.7 kJ mol-1

        • -90.7 kJ mol-1

        Choose your answer

        4
        1 mark

        A series of experiments was carried out on a reaction involving compounds A, B and C and the following results were obtained.

        Experiment

        Initial concentration of A / mol dm-3

        Initial concentration of B / mol dm-3

        Initial concentration of C / mol dm-3

        Initial rate / mol dm-3 s-1

        1

        0.4

        0.12

        0.42

        3.2 x 10-3

        2

        0.8

        0.24

        0.42

        6.4 x 10-3

        3

        0.4

        0.12

        0.21

        8.0 x 10-4

        4

        1.2

        0.24

        0.84

        3.84 x 10-2

        What is the correct rate equation for this reaction?

        • rate = k[A][C]2

        • rate = k[A]2[B]

        • rate = k[A][B][C]2

        • rate = k[A]2[B][C]

        Choose your answer

        5
        1 mark

        For the reaction between nitric oxide and hydrogen, a possible reaction mechanism is shown below.

        Overall: 2NO (g) + 2H2 (g) → N2 (g) + 2H2O (l)

        Step 1: 2NO (g) → N2O2 (g)

        Step 2: N2O2 (g) + H2 (g) → H2O (l) + N2O (g)

        Step 3: N2O (g) + H2 (g) → N2 (g) + H2O (l)

        Rate = k[NO]2[H2]

        Which statement(s) is / are correct?

        1. The rate of reaction is halved if [NO] is halved and [H2] is doubled.

        2. The second step is the rate-determining step.

        3. The rate constant is independent of temperature.

        • 1, 2 and 3

        • Only 1 and 2

        • Only 2 and 3

        • Only 1

        Choose your answer