Kinetics (AQA A Level Chemistry)

Exam Questions

3 hours45 questions
11 mark

Which of the following factors can affect the value of the activation energy of a reaction?

 

The presence of a catalyst

Changes in temperature

Changes in the concentration of the reactants

A

B

C

D

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    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

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

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

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

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    31 mark

    Why does a mixture of hydrogen gas and chlorine gas react faster at a temperature of 600 K than at 500 K?

     

    A higher proportion of successful collisions occurs at 600 K

    Hydrogen molecules and chlorine molecules collide more frequently at 600 K

    The activation energy of the reaction is lower at 600 K

    A

    B

    C

    D

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      41 mark

      What is the main reason for reaction rate increasing as temperature increases?

      • The activation energy decreases

      • The activation energy increases

      • More molecules have an energy ≥ the activation energy

      • The molecules collide more frequently

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      51 mark

      This energy profile diagram represents the reaction pathway for the following reaction:

      Y (g) + Z (g) → W (g) + X (g)10-3

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

      • It will have a negative ΔH

      • It will have a positive ΔH

      • It will have a smaller activation energy

      • The temperature of the surroundings increase

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      61 mark

      This question concerns the Maxwell-Boltzmann energy distribution shown below.

      l6MxV2dH_6

      How does the curve change when the temperature is increased?

      • Stays the same

      • Peak height decreases and moves to the left

      • Peak height increases and moves to the right

      • Peak height decreases and moves to the right

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      71 mark

      The Maxwell–Boltzmann distribution for a sample of a gas, Z, at two different temperatures, T1 and T2, is shown.

      eVlqSWD9_8

      Which letter represents the mean energy of molecules at a higher temperature?

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        81 mark

        The Maxwell-Boltzman distribution of molecular energies in a sample of gas is shown.

        h9t9An5R_2

        What does the area underneath the curve represent?

        • The number of particles which can react with each other

        • The total number of particles

        • The total energy of the particles

        • The total number of particles that have activation energy

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        91 mark

        The Maxwell-Boltzman distribution of molecular energies in a sample of gas is shown.

        YUhzs3Q~_3

        What effect would adding a catalyst have on the activation energy, Ea?

        • Move to the left and the peak would be unchanged

        • Move to the left and the peak would move to the right

        • Move to the left and the peak would move to the left

        • The activation energy would be unchanged and the peak move to the right

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        101 mark

        The Maxwell-Boltzman distribution of molecular energies in a sample of gas is shown.

        KvMLP2Bh_10

        What does the shaded area represent?

        • The total number of particles that do have enough energy to react

        • The total number of particles that do not have enough energy to react

        • The total number of particles that do have enough energy to react in the presence of a catalyst

        • The total number of particles that do not have enough energy to react in the presence of a catalyst

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        11 mark

         The Maxwell-Boltzmann distribution of molecular energies in a sample of a gas at a given temperature is shown.

        131

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

        • X will shift up and to the left showing that fewer molecules possess the most probable energy 

        • X will shift down and to the right showing that fewer molecules possess the most probable energy 

        • X will shift left showing that more molecules possess the most probable energy 

        • X will remain the same but the area under the distribution curve increases

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        21 mark

        The reaction pathway for an endothermic reaction is shown.

        141

        Which arrow represents the activation energy for the reverse reaction?

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          31 mark

          The dotted-line curve on each graph below represents the corresponding Maxwell-Boltzmann distribution for a gas at 200 K. 

          Which solid-line curve most accurately represents the Maxwell-Boltzmann distribution of molecular energies in the same gas at 400 K?

          • N-SXe8-c_21

          • 1t389Mf3_22

          • -ccMdHTu_23

          • bI91Tu1S_24

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          41 mark

          The reaction pathway shows the energies of the reactants, the products and the transition state of a reaction.

          P03b8Dte_25

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

          • E3 – E2

          • E2 – E1

          • E2 – E3

          • E1 – E2

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          51 mark

          The Maxwell-Boltzmann distribution of the kinetic energies of molecules in a slowly reacting gaseous mixture, without a catalyst, at a given temperature is shown. 

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

          -gm7M2OT_1-1

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

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            61 mark

            Four possible reactions (A, B, C and D) of the following equation are measured at the same temperature.

            X (g) + Y (g) → Z (g)

            Which reaction pathway diagram shows the reaction occurring rapidly with an overall negative enthalpy value?

            • s_4XBiaG_27

            • EggvSvnj_28

            • HVkkGJek_29

            • -76wKKWa_30

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            71 mark

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

            2-1

            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 right

            • 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 left

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

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            81 mark

            The Maxwell-Boltzmann distribution of the distribution of molecular energies in sample 1 of a gas is shown.

            NaPhFd9F_5-1

            A change was made to the reaction conditions, as shown by the dotted curve, labelled sample 2.

            What factor was changed in the reaction conditions to produce the dotted curve, labelled sample 2? 

             

            Temperature increased

            Catalyst added

            Volume reduced

            A

            B

            C

            D

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              91 mark

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

              Reaction 1: 1.5 g of solid calcium carbonate is added to 100 cm3 of 0.5 mol dm-3 hydrochloric acid.

              Reaction 2: 100 cm3 of distilled water is added to 100 cm3 of 0.5 mol dm-3 hydrochloric acid and then 1.5 g 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 as a result of adding water? 

               

              Frequency of collisions between reactant molecules is reduced

              Proportion of effective collisions between reactant molecules is reduced

              Proportion of reactant molecules possessing the activation energy is reduced

              A

              B

              C

              D

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                101 mark

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

                1gU3wNWg_31

                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

                increases

                decreases

                B

                decreases

                decreases

                decreases

                C

                increases

                decreases

                increases

                D

                increases

                decreases

                decreases

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                  11 mark

                  In a sealed container, a mixture of gases reacted together at 300 K. The temperature was then increased to 400 K as shown on the Maxwell-Boltzmann distribution curve.

                  8mRjhYdc_13

                  Which of the following statements are correct about the reaction at 400 K?

                   

                  All reacting molecules have greater kinetic energy

                  The most probable energy value, Emp will be higher

                  The area under the curve has increased

                  More particles have energy ≥ Ea

                  A

                  B

                  C

                  D

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                    21 mark

                    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.

                    AM-gzNAQ_33

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

                    • Increase the temperature

                    • Add 0.1 mol dm–3 hydrogen peroxide

                    • Add water

                    • Add more manganese (IV) oxide

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                    31 mark

                    In a reaction between 1.00 mol dm-3 hydrochloric acid and an excess of calcium carbonate chips, 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 2.00 mol dm-3 hydrochloric acid. 

                    Which line on the graph represents this experiment?

                    34

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                      41 mark

                      The diagrams below shows the Maxwell–Boltzmann distribution of molecular energies in a sample of gas.

                      23

                      In diagram 1, one line, P or Q, corresponds to the activation energy in the presence of a catalyst and the other line corresponds to the activation energy of the same reaction in the absence of a catalyst.

                      In diagram 2, one curve, X or Y, corresponds to a temperature higher than that of the other curve. 

                      Which combination gives the correct curve and line?

                       

                      Presence of catalyst

                      Higher temperature

                      A

                      P

                      X

                      B

                      P

                      Y

                      C

                      Q

                      X

                      D

                      Q

                      Y

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                        51 mark

                        In an experiment 1.0 mol dm-3 H2O2 was reacted with hydrochloric acid at 20 degreeC and the volume of oxygen recorded, as shown by curve 1.

                        The experiment was repeated a second time to produce curve 2.

                        What factor was changed to produce curve 2?

                        33

                        • The temperature was raised to 30 degreeC

                        • A catalyst was used

                        • 0.5 mol dm-3 H2O2 used

                        • The temperature was lowered to 10 degreeC

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                        61 mark

                        Hydrogen will react with chlorine to form hydrogen chloride gas.

                        Apart from increasing temperature, what other two factors could speed up the rate of hydrogen chloride formation?

                         

                        Heterogeneous catalyst

                        Increase the most probable energy, Emp

                        Increase pressure 

                        Decrease pressure

                        A

                        B

                        C

                        D

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                          71 mark

                          Which arrow indicates the activation energy for a catalysed reaction on the reaction profile shown?

                          S~zoFKJC_4

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                            81 mark

                            Consider the Maxwell-Boltzmann distribution curve below.

                            etB77j0g_8

                            What would be the effect on the distribution curve if the number of molecules in the original reaction mixture is increased, but no other changes are made?

                             

                            Area under the curve increases

                            Most probable energy, Emp increases

                            Number of molecules with energy ≥ Ea increases

                            Curve shifts upwards and to the left

                            A

                            B

                            C

                            D

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                              91 mark

                              Consider the Maxwell-Boltzmann distribution of molecular energies for gaseous molecules, with and without a catalyst.

                              jTuucx-o_9

                              What would always result in a decrease in the number of molecules contained within area Y?

                               

                              Decrease pressure

                              Decrease temperature

                              Putting the gas into a smaller container

                              Removing a quarter of the catalyst

                              A

                              B

                              C

                              D

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                                101 mark

                                30.0 cm3 of 0.750 mol dm−3 aqueous ethanoic acid reacts with 390 mg sodium which is the limiting reagent. 

                                Hydrogen gas is produced and collected with a gas syringe.

                                5-1

                                What is the minimum mass, in mg, of sodium required to react?

                                • 259

                                • 5.18 x 10-1

                                • 518

                                • 9.78 x 10-4

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