0%

DP IB Chemistry: SL

Topic Questions

Home / IB / Chemistry: SL / DP / Topic Questions / 7. Equilibrium / 7.1 Equilibrium / Structured Questions: Paper 2


7.1 Equilibrium

Question 1a

Marks: 3
a)
The following dynamic equilibrium was reached at temperature, T, in a closed container.

2X (g) + Y (g) ⇌ 2Z (g)             ΔH = -65 kJ mol-1

The value of Kc for the reaction was 75.0 mol-1 dm3 when the equilibrium mixture contained 2.97 mol of Y and 5.38 mol of Z.

i)
Define dynamic equilibrium.
[2]
ii)
Write an expression for Kc for the reaction.
[1]
    Assess your score
      

    Question 1b

    Marks: 2
    b)

    If the conditions for a closed container are changed, it can affect the concentrations of the reactants, products and Kc

    State the effect, if any, on the concentration of Y at equilibrium if temperature, T, is decreased and give a reason for your answer.

    [2]

      Assess your score
        

      Question 1c

      Marks: 1
      c)
      Calculate the equilibrium constant for the following reaction at temperature, T

      2Z (g) ⇌ 2X (g) + Y (g)

      [1]

        Assess your score
          

        Question 2a

        Marks: 4
        a)

        A 0.680 mol sample of SO3 is introduced into a reaction container and allowed to reach equilibrium at temperature T

        2SO3 (g) ⇌ 2SO2 (g) + O2 (g)                ΔH = +196 kJ mol-1

        The value of Kc for the reaction was 7.9 x 10-3 mol dm-3.

        The size of the container for the reaction is increased. State the effect if any on the equilibrium constant, Kc, and the position of equilibrium. Justify your answer.
        [4]
          Assess your score
            

          Question 2b

          Marks: 3
          b)
          The temperature of the reaction in part (a) is increased. State the effect, if any, on the equilibrium constant, Kc, and the position of equilibrium. Justify your answer.
          [3]
            Assess your score
              

            Question 2c

            Marks: 1
            c)

            If the value of the equilibrium constant, Kc, is 2.7 x 10-2 at temperature T1 for the reaction:

            2SO3 (g) ⇌ 2SO2 (g) + O2 (g)

             Calculate the equilibrium constant, Kc, for the reaction:

            4SO2 (g) + 2O2 (g) ⇌ 4SO3 (g)

            Give your answer to 2 decimal places.

            [1]

              Assess your score
                

              Question 3a

              Marks: 2
              a)

              A mixture in a container at temperature, T, is allowed to reach equilibrium.

              2E (g) ⇌ 2F (g) + G (g)     ΔH = -143 kJ mol-1

              The value of Kc for the reaction at T is 2.98 mol dm-3. Comment on the relationship between the concentration of the reactant E and products F and G with regards to Kc.
              [2]
                Assess your score
                  
                Key Concepts
                The Size of Kc

                Question 3b

                Marks: 1
                b)

                Reactants G and H react together to form products J and K according to the equation

                3G + H ⇌ 4JK

                Write the expression for the equilibrium constant, Kc.
                [1]
                  Assess your score
                    

                  Question 3c

                  Marks: 3
                  c)

                  Diesters are compounds often used as synthetic lubricants for machinery such as compressors. The reaction below shows the formation of a diester from propanoic acid and propane-1,3-diol. 

                  2CH3CH2COOH + HOCH2CH2CH2OH ⇌ C9H16O4 + 2H2O

                  The value for Kc at temperature, T, is 1.29.

                  The forward reaction is slightly exothermic. At a different temperature, T1, the value for Kc increases to 22.78. 

                  State whether the new temperature, T1, is higher or lower than the original temperature. Justify your answer.

                  [3]

                    Assess your score
                      

                    Question 4a

                    Marks: 3
                    a)

                    The graph below shows the effect of pressure and temperature on the equilibrium yield of gaseous molecules.

                    JJZI1Mjr_1

                     

                    Using the graph, explain whether the forward reaction is exothermic or endothermic.

                    [3]

                      Assess your score
                        

                      Question 4b

                      Marks: 3
                      b)

                      Use the graph to explain whether the forward reaction will involve either an increase or decrease in the number of moles of a gas.

                      [3]

                        Assess your score
                          

                        Question 4c

                        Marks: 3
                        c)
                        The graph to show the relationship between temperature and Kc for a different dynamic equilibrium to produce a gaseous product is shown below.

                        GkgJwoUC_2
                         
                        Use the information shown in the graph to establish whether the forward reaction is exothermic or endothermic. Justify your answer.
                        [3]

                          Assess your score