IBChemistryDPHLExam QuestionsHow Much, How Fast & How Far?How Fast? The Rate of Chemical Change

How Fast? The Rate of Chemical Change (DP IB Chemistry: HL): Exam Questions

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11 mark

Which of the following factors will not affect the value of the activation energy of a reaction?

I. The presence of a catalyst.

II. Changes in temperature.

III. Changes in the concentration of the reactants.

  • I and II only

  • I and III only

  • II and III only

  • I, II and III

Choose your answer

21 mark

The oxidation of butadiene, CH2=CHCH=CH2, using air or oxygen, produces the molecule crotonaldehyde, CH3CH=CHCHO.

One method of oxidation is to pass a mixture of butadiene and oxygen through a hot aqueous solution of palladium(II) ions, Pd2+(aq), which catalyse the reaction.

Which statement about the action of the Pd2+(aq) ions is not correct?

  • Pd2+(aq) lowers the activation energy for the reaction

  • Pd2+(aq) increases the energy of the reacting molecules

  • When Pd2+(aq) is used, the reaction proceeds by a different route

  • Changing the concentration of the Pd2+(aq) affects the rate of oxidation

Choose your answer

31 mark

The Maxwell-Boltzmann energy distribution curve below describes a mixture of two gases at a given temperature. For a reaction to occur between the gaseous molecules, they must collide with sufficient energy.

Graph showing number of molecules versus energy. Curve peaks midway, with two vertical lines marking energy levels E_a1 and E_a2 on the x-axis.

Of the two activation energy (Ea) values shown, one is for a catalysed reaction, the other for an uncatalysed one.

When a catalyst is used, which pair of statements is correct?

A

Ea1    uncatalysed reaction fewer effective collisions

Ea2      catalysed reaction more effective collisions

B

Ea1    catalysed reaction fewer effective collisions  

Ea2      uncatalysed reaction more effective collisions

C

Ea1      uncatalysed reaction more effective collisions

Ea2      catalysed reaction fewer effective collisions

D

Ea1    catalysed reaction more effective collisions

Ea2      uncatalysed reaction fewer effective collisions

    Choose your answer

    41 mark

    Ammonia is manufactured using the Haber process, which is represented by the following equation:

    N2 (g) + 3H2 (g)  rightwards harpoon over leftwards harpoon  2NH3 (g)                   ∆H = –93 kJ mol–1

    What happens to the rate of the forward and backward reactions when the temperature is increased?

    • there is no effect on the backward or forward rate 

    • both forward and backward rates increase 

    • the forward rate only increases

    • the backward rate only increases

    Choose your answer

    51 mark

    Why does a mixture of hydrogen gas and bromine gas react together faster at a temperature of 500 K than it does at a temperature of 400 K?

    I. A higher proportion of effective collisions occurs at 500 K

    II. Hydrogen molecules and bromine molecules collide more frequently at 500 K

    III. The activation energy of the reaction is lower at 500 K

    • I and II only

    • I and III only 

    • II and III only 

    • I, II and III

    Choose your answer

    61 mark

    When the pressure of a fixed mass of gaseous reactants is raised at a constant temperature, the rate of reaction increases.

    Which statements explain this observation?

    I.Raising the pressure lowers the activation energy.

    II. More molecules have energy greater than the activation energy at the higher pressure.

    III. More collisions occur per second when the pressure is increased.

    • I only

    • I and II only 

    • III only 

    • I, II and III

    Choose your answer

    71 mark

    What is the main reason for the increase in reaction rate with increasing temperature?

    • The activation energy decreases.

    • The activation energy increases.

    • The molecules collide more frequently.

    • More molecules have an energy greater than the activation energy.

    Choose your answer

    81 mark

    The diagram represents the reaction pathway for the following reaction:

    Z(g) + Y(g)  →  X(g) + W(g)

    Energy profile diagram showing reactants Y + Z transforming into products W + X. Activation energy peak between reactants and products along reaction pathway.

    What statement is true about the reverse reaction, W(g) + X(g)  →  Y(g) + Z(g)?

    • it will have a smaller activation energy and a negative ∆H 

    • it will have a smaller activation energy and a positive ∆H 

    • it will have a larger activation energy and a negative ∆H

    • it will have a larger activation energy and a positive ∆H

    Choose your answer

    91 mark

    A student measured the rate of a reaction at two different temperatures: 40°C  and 50°C. They observed that the rate of reaction roughly doubled.

    What explains this observation?

    • raising the temperature by 10°C doubles the average velocity of the molecules 

    • raising the temperature by 10°C doubles the average kinetic energy of each molecule

    • raising the temperature by 10°C doubles the number of molecules having more than a certain minimum energy 

    • raising the temperature by 10°C doubles the number of molecular collisions in a given time

    Choose your answer

    101 mark

    Which statements correctly describe how a catalyst works?

    I. A catalyst does not affect the enthalpy change of the reaction.

    II. A catalyst increases the rate of the reverse reaction.

    III. A catalyst increases the average kinetic energy of the reacting particles.

    • I only

    • I and II only 

    • III only 

    • I, II and III

    Choose your answer

    11
    Sme Calculator    1 mark

    Which of the following statements about the rate-determining step are correct?

    I. It has the highest activation energy.

    II. It can be used to deduce the rate expression.

    III. It is the slowest step in the reaction mechanism.

    • I and II only 

    • I and III only 

    • II and III only

    • I, II and III

    Choose your answer

    12
    Sme Calculator    1 mark

    The rate information below was obtained for the following reaction at a constant temperature: 

    A + 2B → C + 2D

    Experiment 

    Initial [A]  / mol dm–3

    Initial [B]  / mol dm–3

    Initial rate / mol dm–3 s–1

    1

    0.25

    0.25

    3.5 x 10-4

    2

    0.25

    0.50

    To be calculated

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

    What is the initial rate of reaction for experiment 2, in mol dm–3 s–1?

    • 1.4 x 10-3 

    • 7.0 x 10-4

    • 3.5 x 10-4 

    • 1.75 x 10-4

    Choose your answer

    13
    Sme Calculator    1 mark

    The rate equation for the reaction between A and B is:

    Rate = k [A] [B]

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

    • mol-1 dm3 s-1

    • mol−2 dm6 s−1

    • mol2 dm−6 s−1

    • mol dm-3 s-1

    Choose your answer

    14
    Sme Calculator    1 mark

    The rate information below was obtained for the following reaction at a constant temperature: 

    5Br– (aq) + BrO3– (aq) + 6H+ (aq) → 3Br2 (aq) + 3H2O (l)

    Graph showing reaction rate versus hydrogen ion concentration. Curve rises steeply, indicating increased reaction rate as concentration of H+ increases.

    What is the order of reaction with respect to [H+]?

    • One

    • Two

    • Six

    • Zero

    Choose your answer

    15
    Sme Calculator    1 mark

    The mechanism for the following reaction between nitrogen(IV) oxide and carbon monoxide is shown.

    NO2 (g) + CO (g) → NO (g) + CO2 (g)

    Step 1:   NO2 + NO2 → NO3 + NO   slow step

    Step 2:   NO3 + CO → NO2 + CO2   fast step

    What rate expression is consistent with the mechanism?

    • Rate = k [NO2] [CO]

    • Rate = k [NO3] [CO]

    • Rate = k [NO2]2

    • Rate = k [NO2]

    Choose your answer

    16
    Sme Calculator    1 mark

    The solid line in the graph below represents the Arrhenius plot for a reaction.

    Graph with four lines labelled A to D, plotting ln k against 1/T. Lines slope downwards with varying steepness, indicating different rates.

    Which labelled line represents the reaction with the highest activation energy?

      Choose your answer

      17
      Sme Calculator      1 mark

      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

      Choose your answer

      18
      Sme Calculator      1 mark
      Graph showing ln K vs 1/T with a descending trend line across five plotted data points on a grid background, ranging from -4.5 to -8.0 on ln K axis.

      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

      Choose your answer

      19
      Sme Calculator      1 mark

      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

        Choose your answer

        20
        Sme Calculator        1 mark
        Graph showing a line plot of ln k versus 1/T (K⁻¹) with a negative slope. Data points are marked with crosses on a grid background.

        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

        Choose your answer

        11 mark

        The distribution of molecular energies in a sample of a gas at a given temperature is shown by the Boltzmann distribution graph below.

        Graph showing the distribution of molecular energy with a curve peaking at point X. Y-axis: Number of molecules, X-axis: Molecular energy.

        If the temperature is increased, what will happen to the position of point X?

        • fewer molecules possess the most probable energy value so X will shift to the right 

        • fewer molecules possess the most probable energy value so X will shift to the left

        • more molecules possess the most probable energy value so X will shift to the left

        • the position of X will stay the same but the area under the distribution curve increases

        Choose your answer

        21 mark

        The diagram shows a reaction pathway for an endothermic reaction.

        Which arrow represents the activation energy for the forward reaction?

        eAOwD8WJ_8

          Choose your answer

          31 mark

          The dotted-line curve on each graph below represents the corresponding distribution for a gas at 300 K.

          Which solid-line curve most accurately represents the distribution of molecular energies in the same gas at 500 K?

          Four graphs, labelled A to D, show number of molecules versus molecular energy with solid and dashed curves depicting different energy distributions.

            Choose your answer

            41 mark

            The energies of the reactants, the products and the transition state of a reaction are shown in the reaction pathway diagram below.

            Graph showing a reaction energy diagram, with reactants starting at E2, rising to a transition state at E3, and ending at products level E1.

            Which expression correctly represents how to calculate the activation energy of the forward reaction?

            • E1 – E2

            • E2 – E1

            • E2 – E3

            • E3 – E2

            Choose your answer

            51 mark

            The diagram below represents, for a given temperature, the Boltzmann distribution of the kinetic energy of the molecules in a mixture of two gases that react slowly together without a catalyst.

            The activation energy for the reaction, Ea, is marked for the uncatalysed reaction

            What would the position of Ea be if the reaction took place with an effective catalyst?

            Graph showing a curve for the distribution of molecules against kinetic energy, with points A, B, C, D, and activation energy labelled as Eₐ.

              Choose your answer

              61 mark

              Four possible energy profiles are shown below, for reactions carried out at the same temperature.

              Which energy profile shows a reaction that is likely to proceed most rapidly and with a good yield?

              Four reaction energy diagrams labelled A to D, showing energy changes from reactants to products on graphs with similar axes.

                Choose your answer

                71 mark

                The diagram shows a Boltzmann distribution of molecular energies for a gaseous mixture. The distribution has a peak, labelled Q on the diagram.

                Graph showing distribution of molecular energy; y-axis is number of molecules, x-axis is molecular energy, peak at Q, activation energy marked at Eₐ.

                What happens when an effective catalyst is added to the mixture?

                • the height of the peak remains the same, and the activation energy moves to the left 

                • the height of the peak decreases and the activation energy moves to the left

                • the height of the peak remains the same, and the activation energy moves to the right

                • the height of the peak decreases and the activation energy moves to the right

                Choose your answer

                81 mark

                A student performs two reactions and measures the rate of product formation.

                Reaction 1: 1.5g of solid calcium carbonate is added to 100 cm3 of 0.5 M hydrochloric acid

                Reaction 2: 100 cm3 of distilled water is then added to 100 cm3 of 0.5 M hydrochloric acid then 1.5g of solid calcium carbonate is added

                The rate of reaction 1 was faster than the rate of reaction 2.

                Which of the following 3 hypotheses correctly describes the difference in the rate?

                I. Adding water reduces the frequency of collisions between reactant molecules.

                II. Adding water reduces the proportion of effective collisions between reactant molecules.

                III. Adding water reduces the proportion of reactant molecules possessing the activation energy.

                • I only

                • I and II only 

                • III only 

                • I, II and III

                Choose your answer

                91 mark

                The Boltzmann distribution shows the number of molecules that have particular kinetic energy at a constant temperature.

                Graph showing distribution of gas molecules by kinetic energy. Y-axis: number of molecules, X-axis: kinetic energy. Areas marked H, J, K, with Ea labelled.

                If the temperature is decreased by 10 degreeC, what happens to the size of the areas labelled H, J and K?

                 

                H

                J

                K

                A

                decreases

                decreases

                decreases

                B

                decreases

                increases

                decreases

                C

                increases

                decreases

                decreases

                D

                increases

                decreases

                increases

                  Choose your answer

                  101 mark

                  Zinc reacts with copper sulfate according to the following equation:

                  Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4 (aq)

                  Rates of reaction can be found by measuring how certain properties change during the course of the reaction. Which of these properties could be used?

                  I. Change in volume.

                  II. Change in temperature.

                  III. Change in colour.

                  • I and II only

                  • I and III only

                  • Ii and III only

                  • I, II and III

                  Choose your answer

                  111 mark

                  Which of the following statements about the rate constant, k, are correct? 

                  I. High values of k are associated with fast reactions

                  II. The rate constant is affected by temperature

                  III.  The units of k are independent of the orders of reaction

                  • I and II only

                  • I and III only

                  • II and III only

                  • I, II and III

                  Choose your answer

                  121 mark

                  A student experimentally determined the rate expression for the reaction between iodine and propanone to be: 

                  Rate = k [H+] [C3H6O] 

                  Which graph is consistent with this information?

                  Graph showing curves of reaction rate vs. propanone concentration. Lines labelled A, B, C, D represent different reaction rates and concentrations.

                    Choose your answer

                    131 mark

                    The rate information below was obtained for the following reaction at a constant temperature: 

                    C2H5Br (aq) + OH- (aq) → C2H5OH (aq) + Br - (aq)

                    [C2H5Br] / mol dm-3

                    [OH-] / mol dm-3

                    Rate / mol dm-3 s-1

                    3.0 x 10-3

                    2.0 x 10-2

                    4.0 x 10-4

                    6.0 x 10-3

                    2.0 x 10-2

                    8.0 x 10-4

                    6.0 x 10-3

                    4.0 x 10-2

                    1.6 x 10-3

                    What are the orders of reaction with respect to C2H5Br and OH-?

                    • C2H5Br is first order and OH- is first order 

                    • C2H5Br is first order and OH- is second order

                    • C2H5Br is second order and OH-is first order

                    • C2H5Br is second order and OH- is second order

                    Choose your answer

                    141 mark

                    The mechanism for the following reaction between iodine and propanone is shown. 

                    CH3COCH3 (aq) + I2 (aq) → CH3COCH2I (aq) + HI (aq)

                    Step 1: CH3COCH3 + H+ → CH3COH+CH3        

                    Step 2: CH3COH+CH3 → CH3COHCH2 + H+ 

                    Step 3: CH3COHCH2 + I2 → CH3COHCH2I + I-

                    Step 4: CH3COHCH2I → CH3COCH2I + H+ 

                    Which classifications of CH3COCH3, H+ and CH3COHCH2 are correct?

                     

                    CH3COCH3

                    H+

                    CH3COHCH2

                    A

                    Intermediate

                    Intermediate

                    Catalyst

                    B

                    Reactant

                    Intermediate

                    Product

                    C

                    Reactant

                    Catalyst

                    Intermediate

                    D

                    Reactant

                    Product

                    Intermediate

                      Choose your answer

                      151 mark

                      The proposed mechanism for the following reaction where ethanal dimerises in dilute alkaline solution to form 3-hydroxybutanal is shown. 

                      2CH3CHO → CH3CH(OH)CH2CHO

                      Step 1: CH3CHO + :OH- → :CH2CHO + H2O                                       slow step

                      Step 2: CH3CHO + :CH2CHO → CH3CH(O:-)CH2CHO                        fast step

                      Step 3: CH3CH(O:-)CH2CHO + H2O → CH3CH(OH)CH2CHO + :OH-  fast step

                      Which of the following statements is not correct?

                      • The rate expression is rate = [CH3CHO] [OH-]

                      • Step 1 is the rate-determining step

                      • OH- is a catalyst

                      • Steps 2 and 3 have a lower activation energy than step 1

                      Choose your answer

                      161 mark
                      Graph showing a linear relationship between ln k and 1/T (K⁻¹) with data points and a trend line, ranging from ln k -10 to -5 and 1/T 2.60 to 3.30.

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

                      I. The gradient has a value of Ea / R.

                      II.  The intercept on the y-axis is ln A.

                      III. 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

                      Choose your answer

                      171 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)

                      Choose your answer

                      181 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

                       What is the temperature of the reaction?

                      • 300

                      • 330

                      • 280

                      • 430

                      Choose your answer

                      191 mark

                      Which statements are correct?

                      I. Many reactions show a doubling of the rate with a temperature increase of 10 K.

                      II. The units of k for a second order reaction are mol-1 dm3 s-1.

                      III. In the Arrhenius equation, A relates to the energy requirements of the collisions.

                      • I and II only

                      • I and III only

                      • II and III only

                      • I, II and III

                      Choose your answer

                      201 mark

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

                      Four graphs labelled A to D. A shows an increasing curve, B a straight upward line, C a decreasing curve, and D a straight downward line.

                        Choose your answer

                        11 mark

                        In a reaction between 1M hydrochloric acid and an excess of marble chips (calcium carbonate) the volume of gas produced was measured against time. This is shown on the dotted line in the graph below.

                        The experiment was repeated, but this time using the same volume of 2M hydrochloric acid. Which line on the graph represents this experiment?

                        Graph showing the volume of CO2 produced over time with four lines labelled A to D, demonstrating different rates and levels of CO2 production.

                          Choose your answer

                          21 mark

                          1 dm3 of gas X and 1 dm3 of gas Y are kept at the same temperature and pressure.

                          The speed of the molecules is plotted against the fraction of molecules with that speed. From the graph what can be said about the two gases?

                          Graph showing two curves, X and Y, representing the fraction of particles against molecular speed. X peaks higher and shifts left compared to Y.

                          • The molar mass of X is larger than the molar mass of Y

                          • The molar mass of Y is larger than the molar mass of X

                          • The average kinetic energy of X is higher than that of Y

                          • The average kinetic energy of Y is higher than that of X

                          Choose your answer

                          31 mark

                          A beaker containing 100 cm3 of 2M sulfuric acid, H2SO4 (aq), was placed on a balance and then an excess of powdered zinc was added. The change in mass was recorded against time and the results plotted on a graph as shown in line I below.

                          What change in conditions could result in line II shown on the graph?

                          Graph showing two downward curves labelled I and II, representing mass decreasing over time. Curve II is below curve I. Axes labelled Mass and Time.

                          • Using twice as much powdered Zn

                          • Using pieces of zinc that have the same mass as the powder

                          • Raising the temperature of the sulfuric acid, H2SO4 (aq)

                          • Using more concentrated H2SO4 (aq), but keeping the volume the same

                          Choose your answer

                          41 mark

                          Bleach solution contains sodium chlorate (I) which naturally decomposes according to the equation below:

                          2NaClO (aq)  → 2NaCl (aq)  +  O2 (g)

                          The bleach decomposes faster as the temperature increases. A 100 cm3 sample of 10% bleach was heated to 40 degreeC and the amount of oxygen evolved was measured against time.

                          The experiment was repeated under the same conditions, but this time using a 100 cm3 sample of 20% bleach. If the first experiment produces the dotted line, which line is produced by the second experiment?

                          Graph showing four curves labelled A to D, depicting volume of oxygen gas over time. Curve A is highest, followed by B, C, and lowest is D.

                            Choose your answer

                            51 mark

                            How does the average kinetic energy of a gas vary with temperature?

                            Four graphs A-D show average kinetic energy vs temperature. A: plateau curve; B: upward curve; C: linear decline; D: linear increase.

                              Choose your answer

                              61 mark

                              Three batches of sulfuric acid containing different volumes and concentrations were reacted with an excess of zinc powder. The hydrogen evolved was measured against time and the results were plotted on a graph. Which lines on the graph could correspond to the specified volumes and concentrations of the sulfuric acid shown in the table?

                              Graph showing volume of hydrogen gas over time, with four curves labelled I to IV. Each curve reaches a maximum volume at different rates and times.

                               

                               

                              25 cm3 of 1.0 M H2SO4

                              50 cm3 of 0.5 M H2SO4

                              25 cm3 of 0.5 M H2SO4

                              A

                              I

                              III

                              IV

                              B

                              I

                              IV

                              III

                              C

                              I

                              II

                              III

                              D

                              II

                              I

                              III

                                Choose your answer

                                71 mark

                                When 1 cm3 of 0.1 mol dm–3 HCl is added to 10 cm3 of 0.02 mol dm–3 Na2S2O3 solution, a pale yellow precipitate forms slowly.

                                When the experiment is repeated with 1 cm3 of 0.1 mol dm–3 HCl and 10 cm3 of 0.05 mol dm–3 Na2S2O3 the precipitate forms more quickly.

                                Why is this?

                                • when 0.05 mol dm–3 Na2S2O3 is used the reactant particles collide more frequently 

                                • when 0.05 mol dm–3 Na2S2O3 is used the collisions between reactant particles are more violent 

                                • when 0.05 mol dm–3 Na2S2O3 is used the activation energy of the reaction is lower 

                                • when 0.05 mol dm–3 Na2S2O3 is used the reaction proceeds by a different pathway 

                                Choose your answer

                                81 mark

                                On the graph, curve 1 was produced from measuring the decomposition of 100 cm3 of 1.0 mol dm–3 hydrogen peroxide in the presence of a manganese (IV) oxide catalyst.

                                Graph showing volume of oxygen formed over time with two curves; curve 1 has a steeper slope initially than curve 2, both plateau at the same level.

                                Which alteration to the original experimental conditions would produce curve 2?

                                • raising the temperature 

                                • adding more manganese (IV) oxide

                                • using more concentrated hydrogen peroxide 

                                • add some 0.1 mol dm–3 hydrogen peroxide

                                Choose your answer

                                91 mark

                                The stoichiometry of a catalysed reaction is shown by the equation below.

                                R (g) + S (g)  ⇌ T (g) + U (g)

                                Two experiments were carried out in which the amount of product T was measured against time. The results are shown in the diagram below.

                                Graph showing two lines for Experiment 1 and Experiment 2 plotting Amount of T over Time. Experiment 1 line plateaus higher than Experiment 2.

                                Which changes in the conditions from experiment 1 to experiment 2 might explain the results shown?

                                I. Product U was continuously removed from the equilibrium mixture.

                                II. A different catalyst was used.

                                III. Less of reactant R was used

                                • I and II only

                                • I and III only

                                • II and III only

                                • I, II and III

                                Choose your answer

                                101 mark

                                Boltzmann distributions are shown in the two diagrams below.

                                Two graphs showing molecular energy distribution. Diagram 1 has points P and Q. Diagram 2 has peaks X and Y, with a solid and a dashed curve.

                                Diagram 1 shows the effect of a catalyst on activation energy.

                                Diagram 2 shows the effect of temperature on the energy distribution.

                                Which row correctly identifies the catalysed activation energy in Diagram 1 and the higher temperature curve in Diagram 2?

                                 

                                presence of catalyst

                                higher temperature

                                A

                                P

                                X

                                B

                                P

                                Y

                                C

                                Q

                                X

                                D

                                Q

                                Y

                                  Choose your answer

                                  11
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                                  The potential energy level profile for the hydrolysis of a tertiary halogenoalkane is shown.

                                  Graph of potential energy versus reaction progress, showing energy peak between reactants and products, indicating an activation energy barrier.

                                  Which of the following conclusions can be deduced from the potential energy level profile?

                                  I. The reaction proceeds via an SN1 mechanism 

                                  II. The reactants are more stable than the products

                                  III. The rate-determining step is the first step of the reaction mechanism

                                  • I and II only 

                                  • I and III only 

                                  • II and III only

                                  • I, II and III

                                  Choose your answer

                                  12
                                  Sme Calculator                                  1 mark

                                  The rate information below was obtained for the following fourth order reaction at a constant temperature: 

                                  5Br– (aq) + BrO3– (aq) + 6H+ (aq) → 3Br2 (aq) + 3H2O (l)

                                  Graph showing a curve increasing exponentially. X-axis: [H⁺] concentration in mol dm⁻³. Y-axis: Reaction rate in mol dm⁻³ s⁻¹.
                                  time-v-conc-graph-bromide-ions

                                  Which rate expression is consistent with the data?

                                  • Rate = k [Br-] [BrO3-] [H+]

                                  • Rate = k [Br-]2 [H+]2

                                  • Rate = k [Br-] [BrO3-] [H+]2

                                  • Rate = k [Br-]2 [BrO3-] [H+]

                                  Choose your answer

                                  13
                                  Sme Calculator                                  1 mark

                                  The rate information below was obtained for the following reaction at a constant temperature: 

                                  C2H5Br (aq) + OH– (aq) → C2H5OH (aq) + Br– (aq)

                                  [C2H5Br] / mol dm-3

                                  [OH-] / mol dm-3 

                                  Rate / mol dm-3 s-1

                                  2.0 x 10-3

                                  1.0 x 10-2

                                  4.0 x 10-4 

                                  4.0 x 10-3

                                  1.0 x 10-2

                                  8.0 x 10-4 

                                  8.0 x 10-3

                                  2.0 x 10-2

                                  3.2 x 10-3 

                                  What is the correct equation to calculate the value of the rate constant, k?

                                  • fraction numerator rate over denominator left square bracket straight C subscript 2 straight H subscript 5 Br right square bracket space left square bracket OH to the power of minus right square bracket end fraction

                                  • fraction numerator left square bracket straight C subscript 2 straight H subscript 5 Br right square bracket space left square bracket OH to the power of minus right square bracket over denominator rate end fraction

                                  • fraction numerator rate over denominator left square bracket straight C subscript 2 straight H subscript 5 Br right square bracket space left square bracket OH to the power of minus right square bracket squared end fraction

                                  • begin mathsize 14px style fraction numerator rate over denominator left square bracket straight C subscript 2 straight H subscript 5 Br right square bracket squared space left square bracket OH to the power of minus right square bracket squared end fraction end style

                                  Choose your answer

                                  14
                                  Sme Calculator                                  1 mark

                                  The mechanism for the following reaction between nitrogen(II) oxide and carbon monoxide is shown.

                                  NO2 (g) + CO (g) → NO (g) + CO2 (g)

                                  Step 1:   NO2 + NO2 ⇌ N2O4   fast step

                                  Step 2:   N2O4 + 2CO → 2NO + 2CO2   slow step

                                  Which rate expression is consistent with the mechanism?

                                  • Rate = k [NO2] [CO]2

                                  • Rate = k [N2O4] [CO]2

                                  • Rate = k [NO2]2 [CO]2

                                  • Rate = k [N2O4] [CO]

                                  Choose your answer

                                  15
                                  Sme Calculator                                  1 mark

                                  The rate information below was obtained for the following reaction of aqueous solutions of F and G, in the presence of a homogeneous catalyst, H, 

                                  2F + 3G → J + 2K

                                  When the concentrations of F and G are doubled, the rate of reaction increases by a factor of four.

                                  When the concentrations of F and H are doubled, the rate of reaction increases by a factor of eight.

                                  Which rate expression is consistent with the data?

                                  • Rate = k [F]2 [G]3

                                  • Rate = k [F]2 [H]

                                  • Rate = k [F] [G] [H]

                                  • Rate = k [F]2 [H]2

                                  Choose your answer

                                  16
                                  Sme Calculator                                  1 mark

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

                                  I. It is a steric factor for the fraction of collisions where the particles have the correct mutual orientation

                                  II. It takes into account the energy of the colliding particles

                                  III. 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

                                  Choose your answer

                                  17
                                  Sme Calculator                                  1 mark

                                  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

                                   What is the value of the constant, A?

                                  • 1.03 x 1015

                                  • 2.57 x 109

                                  • 2.48 x 103

                                  • 3.88 x 101

                                  Choose your answer

                                  18
                                  Sme Calculator                                  1 mark
                                  Graph showing a linear relationship between ln K on the y-axis and 1/T (K⁻¹) on the x-axis, with a descending line crossing multiple data points.

                                   Which is the correct value for the activation energy? (R = 8.31J K–1 mol–1)

                                  • 199 594

                                  • 21 655

                                  • 14 786

                                  • 78 945

                                  Choose your answer

                                  19
                                  Sme Calculator                                  1 mark

                                  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, what is the correct value for the activation energy of the reaction, in J 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

                                  • 11230

                                  • 63400

                                  • 216700

                                  • 52040

                                  Choose your answer

                                  20
                                  Sme Calculator                                  1 mark

                                  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, what activation energy of the reaction in kJ? (R = 8.31J K–1 mol–1)

                                  • 37120

                                  • 481.3

                                  • 10.06

                                  • 1012.5

                                  Choose your answer