Kinetics (Edexcel International A Level Chemistry)

Exam Questions

1a1 mark

The decomposition of ammonia is catalysed by tungsten metal.

2NH3 (g) rightwards arrow with tungsten on top N2 (g) + 3H2 (g)

This reaction has zero order kinetics.

a)
What is the rate equation for this reaction?
  • rate = k

  • rate = k[NH3]

  • rate = k[NH3]2

  • rate = k[N2][H2]3

1b1 mark
b)
What are the units of the rate constant, k, for this zero order reaction?
  • no units

  • s−1

  • mol dm−3 s−1

  • dm3 mol−1 s−1

1c1 mark
c)
Which of these graphs represents this zero order reaction?
q1c-paper-4-oct-2021-edexcel-ial-chemistry

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    11 mark

    The halogenoalkane 2-bromo-2-methylbutane was hydrolysed with sodium hydroxide solution, NaOH (aq).

    Which suggestion about the mechanism of this reaction is correct?

        Type of mechanism Number of steps in mechanism
    A SN2 one
    B SN2 two
    C SN1 one
    D SN1 two

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      21 mark

      Nitrogen monoxide and hydrogen react together to form nitrogen and water.

      2NO + 2H2 → N2 + 2H2O

      The steps in the mechanism of the reaction are

      Step 1  2NO ⇌ N2O2 fast
      Step 2 N2O2 + H2 → N2O + H2O slow
      Step 3 N2O + H2 → N2 + H2O fast

      Which statement about the reaction is correct?

      • Step 3 is the rate determining step and the overall order is 2

      • Step 3 is the rate determining step and the overall order is 4

      • Step 2 is the rate determining step and the overall order is 2

      • Step 2 is the rate determining step and the overall order is 3

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      3
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      1 mark

      The rate equation for a reaction is

      rate = k [A]2 [B]0

      The initial rate of reaction is 9.0 × 10−5 mol dm−3 s−1 when [A] = 0.30 mol dm−3 and [B] = 0.20 mol dm−3.

      What is the value of the rate constant in dm3 mol−1 s−1?

      • 8.1 × 10−6

      • 3.0 × 10−4

      • 1.0 × 10−3

      • 5.0 × 10−3

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      11 mark

      The Arrhenius equation can be shown as

      In k space equals space – E subscript a over R cross times space 1 over T space plus space constant

      A graph is plotted of ln k against 1/T for a reaction.
      The activation energy, Ea , of this reaction equals

      • – gradient ÷ R

      • + gradient ÷ R

      • – gradient × R

      • + gradient × R

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      21 mark

      Propanone reacts with iodine in the presence of a catalyst of dilute hydrochloric acid.
      The reaction occurs in aqueous solution.

      CH3COCH3 + I2 → CH3COCH2I + HI

      The rate equation for this reaction is

      rate = k[CH3COCH3][H+]

      Which is a possible mechanism for the reaction?

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CH subscript 3 straight C left parenthesis straight O with plus on top straight H right parenthesis CH subscript 3 space space space space space space space space space space space space rightwards arrow space CH subscript 3 straight C left parenthesis OH right parenthesis ═ CH subscript 2 space plus space straight H to the power of plus space space space space slow space
CH subscript 3 straight C left parenthesis OH right parenthesis ═ CH subscript 2 space plus space straight I subscript 2 space rightwards arrow space CH subscript 3 COCH subscript 2 straight I space plus space HI space space space space space space space space space space space space space fast

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      • space space space space space space space space CH subscript 3 COCH subscript 3 space space space space rightwards arrow space CH subscript 3 COCH subscript 2 superscript minus plus space straight H to the power of plus space space space space slow space space
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CH subscript 3 COCH subscript 2 superscript minus space plus space straight I to the power of plus space space rightwards arrow space CH subscript 3 COCH subscript 2 straight I space space space space space space space space space space space space space space fast

      • space space space space space space space space space space space space space space space space straight I subscript 2 space space space space space space space space space space space space space space rightwards arrow space straight I to the power of plus space plus space straight I to the power of minus space space space space space space space space space space space space space space space space space space space space space space slow space space
CH subscript 3 COCH subscript 3 space plus space straight I to the power of minus space space rightwards arrow space CH subscript 3 COC space straight H subscript 2 superscript minus space plus space HI space space space slow space space
CH subscript 3 COCH subscript 2 superscript minus space plus straight I to the power of plus space space rightwards arrow space CH subscript 3 COCH subscript 2 straight I space space space space space space space space space space space space space space fast

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