Revision NotesExam QuestionsPast Papers
GCSEScienceEdexcelCombined ScienceChemistryExam QuestionsExtracting Metals & EquilibriaReversible Reactions & Equilibria

Reversible Reactions & Equilibria (Edexcel GCSE Combined Science: Chemistry): Exam Questions

35 mins11 questions
Medium
Hard
1a4 marks

Hydrated copper sulfate, CuSO4.5H2O, is a blue solid. Anhydrous copper sulfate, CuSO4, is a white solid.

Heat energy is needed to convert hydrated copper sulfate to anhydrous copper sulfate. This is a reversible reaction.

 

CuSO4.5H2O rightwards harpoon over leftwards harpoonCuSO4 + 5H2O 

 

Devise an experiment to show that this is a reversible reaction.

How did you do?

1b2 marks

Hydrogen reacts with iodine to form hydrogen iodide. Iodine gas is purple and hydrogen iodide gas is colourless.

H2 (g) + I2 (g) rightwards harpoon over leftwards harpoon 2HI (g) 

Hydrogen and iodine are placed in a sealed container.

The container is left until equilibrium is reached.

The conditions are changed favouring the forward reaction.

Explain what you would see.

How did you do?

1c
Sme Calculator2 marks

Higher Only

Calculate the number of atoms combined in one mole of copper iodide, CuI2. 

(Avogadro constant = 6.02 × 1023)

 number of atoms = ..............................................................

How did you do?

Did this page help you?

21 mark

The Haber process is an example of a reversible reaction where the forward reaction is exothermic:

N2 (g) + 3H2 (g) rightwards harpoon over leftwards harpoon 2NH3 (g)

What is not true about this system when it is at equilibrium?

☐

A

The energy change of the reverse reaction is endothermic

☐

B

The equilibrium occurs within a closed system

☐

C

The reaction has reached completion and stopped

☐

D

The rate of the forward reaction is equal to the rate of the reverse reaction

    Choose your answer

    Did this page help you?

    31 mark

    Which graph shows the highest yield of products?

    ☐

    A

    graph-a

    ☐

    B

    graph-b

    ☐

    C

    graph-c

    ☐

    D

    None of the above

      Choose your answer

      Did this page help you?

      4a4 marks

      In industry, ammonia is manufactured by reacting nitrogen with hydrogen.

      i) Give the name of the industrial process used to manufacture ammonia.

      (1)

      ii) Write the word equation for this reaction, including the correct symbol to show that the reaction is reversible.

      (3)

      How did you do?

      4b1 mark

      The formula of ammonia is NH3.

      State what the formula of ammonia shows about the number of nitrogen atoms and the number of hydrogen atoms combined in a molecule of ammonia.

      How did you do?

      4c3 marks

      Most of the ammonia manufactured in industry is used to produce fertilisers.

      i) A fertiliser is made by reacting ammonia with nitric acid.

      What is the name of this fertiliser?

      (1)

      ☐

      A

      ammonia nitrate

      ☐

      B

      ammonia nitric 

      ☐

      C

      ammonium nitrate 

      ☐

      D

      ammonium nitric 

      ii) Explain the importance of fertilisers in farming. (2)

      How did you do?

      Did this page help you?

      51 mark

      Which is not true about the Haber process for making ammonia?

      ☐

      A

      Platinum is used as a catalyst

      ☐

      B

      The process is carried out at a temperature if 450 oC

      ☐

      C

      The process takes place at a pressure of about 200 atmospheres

      ☐

      D

      Natural gas is a raw material

        Choose your answer

        Did this page help you?

        61 mark

        What does the graph show about the effect of pressure and temperature on the Haber process?

        10-4

        ☐

        A

        Less ammonia is produced at higher pressures

        ☐

        B

        The yield of ammonia decreases with increased temperature

        ☐

        C

        The optimum conditions are low pressure and high temperature

        ☐

        D

        At 500 atmospheres and 400 oC the yield of ammonia is 45%

          Choose your answer

          Did this page help you?

          71 mark

          Higher Only

          The decomposition of ammonium chloride is endothermic:

          NH4Cl (s) rightwards harpoon over leftwards harpoonNH3 (g) + HCl (g)

          Which changes to the conditions would both decrease the amount of product in this reaction?

           

           

          Change 1

          Change 2

          ☐

          A

          Increase pressure

          Decrease temperature

          ☐

          B

          Decrease pressure

          Decrease temperature

          ☐

          C

          Increase pressure

          Increase temperature

          ☐

          D

          Decrease pressure

          Increase temperature

            Choose your answer

            Did this page help you?

            81 mark

            Which option shows two correct statements about reversible reactions and equilibrium?

             

             

            Statement 1

            Statement 2

            ☐

            A

            The sign for a reversible reaction is rightwards harpoon over leftwards harpoon

            Reversible reactions are slower than non-reversible ones

            ☐

            B

            At equilibrium the rate of the forward reaction and the rate of the reverse reaction are equal

            An endothermic reaction is exothermic if reversed

            ☐

            C

            Reversible reactions are not useful in industry as they do not go to completion

            To reach an equilibrium the reaction must occur in a closed system

            ☐

            D

            The rate of the reaction is zero at equilibrium

            The concentration of the product is constant at equilibrium

              Choose your answer

              Did this page help you?

              91 mark

              Higher Only

              The gasification of carbon is a reversible endothermic reaction:

              C (s) + H2O (g) rightwards harpoon over leftwards harpoon CO (g) + H2 (g)

              Which of the following conditions could be changed to increase the relative amount of H2 gas produced?

              ☐

              A

              Increase the surface area to volume ratio of the carbon

              ☐

              B

              Increase the pressure

              ☐

              C

              Increase the temperature

              ☐

              D

              Add a catalyst

                Choose your answer

                Did this page help you?

                16 marks

                Higher Only

                The reaction to produce sulfur trioxide reaches an equilibrium.

                 

                2SO2 (g) + O2 (g) rightwards harpoon over leftwards harpoon2SO3 (g) 

                 

                The forward reaction is exothermic. The rate of attainment of equilibrium and the equilibrium yield of sulfur trioxide are affected by pressure and temperature.

                A manufacturer considered two sets of conditions, A and B, for this reaction.

                In each case sulfur dioxide is mixed with excess oxygen. The manufacturer changed the temperature and the pressure and only used a catalyst in B.

                The sets of conditions A and B are shown in Figure 7.

                set of conditions

                pressure in atm

                temperature in °C

                catalyst

                A

                2

                680

                no catalyst used

                B

                4

                425

                catalyst used

                Figure 7

                The manufacturer chooses set of conditions B rather than set of conditions A.

                Explain, by considering the effect of changing the conditions on the rate of attainment of equilibrium and on the equilibrium yield of sulfur trioxide, why the manufacturer chooses the set of conditions B rather than the set of conditions A.

                (6)

                How did you do?

                Did this page help you?

                26 marks

                Higher Only

                The hydrogen used in a hydrogen-oxygen fuel cell can be produced from methanol, CH3OH.

                CH3OH + H2O rightwards harpoon over leftwards harpoon for blank of CO2 + 3H2

                In this reaction the forward reaction is endothermic and heat energy is taken in from the surroundings. The conditions used for this reaction are

                • a nickel catalyst

                • a temperature of 220 °C

                Explain, in terms of their effects on the rate of attainment of equilibrium and the equilibrium yield of hydrogen, why the reaction is carried out using a catalyst at 220 °C rather than without a catalyst at a lower temperature.

                (6)

                How did you do?

                Did this page help you?