IBChemistry: HLDPExam Questions16. Chemical Kinetics (HL only)16.2 Activation Energy

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First teaching 2014

Last exams 2024

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Activation Energy (DP IB Chemistry: HL)

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16.2 Activation Energy

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16.2 Activation Energy

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1
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The graph below shows ln k against 1 over T for a general reaction.

HCE15yK1_ln-k-vs-1overt-question

Which of the lines shows the highest activation energy compared to the original graph?

stemW_j6_ln-k-vs-1overt-answer-options

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    2
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    The following information was obtained for the rate constant, k, for a reaction at 298 K.

     

    A

    Ea

    R

    2.57 × 109 s–1

    96.2 kJ mol–1

    8.31 J K–1 mol–1

     

    Which expression correctly represents how to calculate the rate constant, k?

    • 2.57 straight x 10 to the power of 9 space straight x space e to the power of left parenthesis negative 96200 divided by 8.31 space straight x space 298 right parenthesis end exponent

    • 2.57 straight x 10 to the power of 9 space straight x space e to the power of left parenthesis negative 96.2 divided by 8.31 space straight x space 298 right parenthesis end exponent

    • 2.57 straight x 10 to the power of 9 space straight x space e to the power of left parenthesis 8.31 space straight x space 298 divided by negative 96.2 right parenthesis end exponent

    • 2.57 straight x 10 to the power of 9 space straight x space e to the power of left parenthesis 8.31 space straight x space 298 divided by negative 96200 right parenthesis end exponent

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    3
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    example-arrhenius-plot

    Which of the following statements about the Arrhenius plot are not correct?

    • ln A has an approximate value of -4.7

    • The gradient of the line is fraction numerator negative E subscript a over denominator R end fraction

    • The units for the x-axis are K-1

    • The equation of the line is ln k = fraction numerator negative E subscript a over denominator R T end fraction + ln A

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    4
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    Which term from the Arrhenius equation has the incorrect units?

     

    Term 

    Units 

    A.

    Ea 

    J mol-1 

    B.

    R 

    J K-1 mol-1 

    C.

    T 

    K-1

    D.

    e 

    No units

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      5
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      example-arrhenius-plot-2

      What is the gradient of the graph?

      • + Ea

      • - Ea

      • fraction numerator negative space E subscript a over denominator R end fraction

      • fraction numerator plus space E subscript a over denominator R end fraction

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      11 mark

      q1_16-2_medium-activation-energy_mcq_hl_medium

      Which of the following statements about the Arrhenius plot are correct? 

      1.     The gradient has a value of Ea / R
      2.     The intercept on the y-axis is ln A
      3.     The Arrhenius plot will give a value for activation energy in J mol-1

      • I and II only

      • I and III only

      • II and III only

      • I, II and III

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      21 mark

      The following information was obtained for the rate constant, k, for a reaction at 25 OC

      A

      Ea

      R

      2.57 × 109 s–1

      96.2 kJ mol–1

      8.31 J K–1 mol–1

      Which expression correctly represents how to calculate the rate constant, k?

      • k = (2.57 x 109) x e(-96.2 / 8.31×25)

      • k = (2.57 x 109) x e(-96.2 / 8.31×298)

      • k = (2.57 x 109) x e(-96200 / 8.31×25)

      • k = (2.57 x 109) x e(-96200 / 8.31×298)

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      31 mark

      The following experimental data was collected. 

      Activation energy, Ea

      111 kJ mol–1

      Rate constant, k

      1.30 x 10-4  mol-1 dm3 s-1

      Arrhenius constant, A

      4.55 × 1013 mol-1 dm3 s-1

       

      Which expression correctly calculates the temperature of the reaction?

      • T = begin mathsize 14px style fraction numerator 111 over denominator 8.31 cross times left parenthesis l n space 4.55 cross times 10 to the power of 13 minus l n italic space 1.30 cross times 10 to the power of negative 4 end exponent right parenthesis end fraction end style

      • T = begin mathsize 14px style fraction numerator 111 cross times 10 cubed over denominator 8.31 cross times left parenthesis l n space 4.55 cross times 10 to the power of 13 minus l n space 1.30 cross times 10 to the power of negative 4 end exponent right parenthesis end fraction end style

      • T = begin mathsize 14px style fraction numerator 111 cross times 10 cubed over denominator 8.31 cross times left parenthesis l n space 1.30 cross times 10 to the power of negative 4 end exponent minus l n italic space 4.55 cross times 10 to the power of 13 right parenthesis end fraction end style

      • T = begin mathsize 14px style fraction numerator 111 cross times 10 cubed over denominator left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent right parenthesis cross times italic left parenthesis l n space 4.55 cross times 10 to the power of 13 minus l n space 1.30 cross times 10 to the power of negative 4 end exponent right parenthesis end fraction end style

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      41 mark

      Consider the following statements: 

      1. Many reactions show a doubling of the rate with a temperature increase of 10K
      2. The units of k for a second order reaction are mol-1 dm3 s-1
      3. In the Arrhenius equation, A relates to the energy requirements of the collisions 

      Which statements are correct?

      • I and II only

      • I and III only

      • II and III only

      • I, II and III

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      51 mark

      Which graph shows the correct relationship between the rate constant, k, and temperature?

      CGpBBWaM_1

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        1
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        Which of the following statements about the constant A in the Arrhenius equation are correct?

        1. It is a steric factor for the fraction of collisions where the particles have the correct mutual orientation
        2. It takes into account the energy of the colliding particles
        3. It takes into account the number of collisions in a chemical reaction

        • I and II only

        • I and III only 

        • II and III only

        • I, II and III

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        2
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        The following information was obtained for the rate constant, k, for a reaction at 25 oC.

         

        k

        Ea

        R

        3.46 × 10–8 s–1

        96.2 kJ mol–1

        8.31 J K–1 mol–1

         

        Which expression correctly represents how to calculate the constant, A?

        • A equals fraction numerator left parenthesis 3.46 cross times 10 to the power of negative 8 end exponent right parenthesis over denominator e to the power of left parenthesis negative 96.2 space divided by space 8.31 cross times 25 right parenthesis end exponent end fraction

        • A equals fraction numerator left parenthesis 3.46 cross times 10 to the power of negative 8 end exponent right parenthesis over denominator e to the power of left parenthesis negative 96200 divided by 8.31 cross times 298 right parenthesis end exponent end fraction

        • A equals fraction numerator e to the power of left parenthesis negative 96200 divided by 8.31 cross times 298 right parenthesis end exponent over denominator left parenthesis 3.46 cross times 10 to the power of negative 8 end exponent right parenthesis end fraction

        • A equals left parenthesis 3.46 cross times 10 to the power of negative 8 end exponent right parenthesis cross times e to the power of left parenthesis negative 96200 divided by 8.31 cross times 298 right parenthesis end exponent

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        3
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        ImoEHe96_example-arrhenius-plot

         

        Which is the correct expression to calculate the activation energy? (R = 8.31J K–1 mol–1)

        • Ea = fraction numerator 1.90 over denominator 0.00020 end fraction cross times left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent right parenthesis

        • Ea = fraction numerator negative 1.90 over denominator 0.00020 end fraction cross times 8.31

        • Ea = fraction numerator negative 1.90 over denominator 0.00020 end fraction cross times left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent right parenthesis

        • Ea = fraction numerator 1.90 over denominator 0.00020 end fraction cross times 8.31

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        4
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        The rate constant data for a reaction at two different temperatures is shown.

         

        Temperature / oC

        Rate constant / mol-1 dm3 s-1

        5

        6.81 x 10-6 

        35

        6.11 x 10-5

         

        Using the following equation, which expression is the correct calculation for the activation energy of the reaction, in kJ mol-1? (R = 8.31J K–1 mol–1)


        ln k subscript 1 over k subscript 2 space equals space E subscript a over R open parentheses 1 over T subscript 2 minus 1 over T subscript 1 close parentheses

        • E subscript a equals fraction numerator ln fraction numerator 6.11 cross times 10 to the power of negative 5 end exponent over denominator 6.81 cross times 10 to the power of negative 6 end exponent end fraction cross times 8.31 over denominator open parentheses 1 over 308 minus 1 over 278 close parentheses end fraction

        • E subscript a equals fraction numerator ln fraction numerator 6.81 cross times 10 to the power of negative 6 end exponent over denominator 6.11 cross times 10 to the power of negative 5 end exponent end fraction cross times stretchy left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent stretchy right parenthesis over denominator stretchy left parenthesis 1 over 278 minus 1 over 308 stretchy right parenthesis end fraction

        • E subscript a equals fraction numerator ln fraction numerator 6.11 cross times 10 to the power of negative 5 end exponent over denominator 6.81 cross times 10 to the power of negative 6 end exponent end fraction cross times 8.31 over denominator stretchy left parenthesis 1 over 278 minus 1 over 308 stretchy right parenthesis end fraction

        • E subscript a equals fraction numerator ln fraction numerator 6.81 cross times 10 to the power of negative 6 end exponent over denominator 6.11 cross times 10 to the power of negative 5 end exponent end fraction cross times stretchy left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent stretchy right parenthesis over denominator stretchy left parenthesis 1 over 308 minus 1 over 278 stretchy right parenthesis end fraction

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        5
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        When the temperature increases from 25 oC to 55 oC, the rate constant for the reaction increases by a factor of 1.45.

        ln k subscript 1 over k subscript 2 space equals space E subscript a over R stretchy left parenthesis 1 over T subscript 2 minus 1 over T subscript 1 stretchy right parenthesis

        Using the equation above, which expression is the correct calculation for the activation energy of the reaction? (R = 8.31J K–1 mol–1)

        • E subscript a equals fraction numerator open parentheses ln space 1.45 close parentheses cross times open parentheses 8.31 cross times 10 to the power of negative 3 end exponent close parentheses over denominator open parentheses 1 over 55 minus 1 over 25 close parentheses end fraction

        • E subscript a equals fraction numerator stretchy left parenthesis ln space 1.45 stretchy right parenthesis cross times stretchy left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent stretchy right parenthesis over denominator stretchy left parenthesis 1 over 328 minus 1 over 298 stretchy right parenthesis end fraction

        • E subscript a equals fraction numerator open parentheses ln fraction numerator 1 over denominator 1.45 end fraction close parentheses cross times open parentheses 8.31 cross times 10 to the power of negative 3 end exponent close parentheses over denominator open parentheses 1 over 328 minus 1 over 298 close parentheses end fraction

        • E subscript a equals fraction numerator stretchy left parenthesis ln space fraction numerator 1.45 over denominator 1 end fraction stretchy right parenthesis cross times stretchy left parenthesis 8.31 cross times 10 to the power of negative 3 end exponent stretchy right parenthesis over denominator stretchy left parenthesis 1 over 55 minus 1 over 25 stretchy right parenthesis end fraction

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