O LevelChemistryCambridge (CIE)Exam Questions5. Chemical Energetics5.1 Exothermic & Endothermic Reactions

Exothermic & Endothermic Reactions (Cambridge (CIE) O Level Chemistry): Multiple Choice Questions

Exam code: 5070

4 hours39 questions

Select a download format for 5.1 Exothermic & Endothermic Reactions

Scroll for more

Select an answer set to view for
5.1 Exothermic & Endothermic Reactions

Easy
Medium
Hard
1
1 mark

The graph below shows a reaction profile for the reaction between methane and oxygen.

A graph with unlabelled axes. A horizontal line on the left is joined by a curve that rises to a peak and then falls to a second horizontal line on the right, which lies below the first. A vertical arrow labelled X runs upwards from the level of the left-hand line to the peak.

What does the label X represent?

  • Activation energy

  • Overall energy change

  • Reactants

  • Progress of the reaction

Choose your answer

2
1 mark

What is the reading on the following thermometer?

A vertical thermometer scale numbered 27, 28 and 29, with five small divisions between each numbered mark. A shaded liquid column rises from below the 27 mark and ends between the 28 and 29 marks.

  • 28.3 oC

  • 28.6 oC

  • 29.2 oC

  • 28.5 oC

Choose your answer

3
1 mark

A student adds a small amount of ammonium chloride to a beaker of water. The temperature of the water decreases from 21 oC to 17 oC.

Which type of process has occurred and why?

type of process

reason

A

exothermic

heat is released

B

exothermic

heat is absorbed

C

endothermic

heat is released

D

endothermic

heat is absorbed

    Choose your answer

    4
    1 mark

    The energy level diagram below shows the relative energies of the reactants and products in a reaction.

    An energy level diagram. The vertical axis is labelled Energy. A horizontal line labelled reactants sits above a horizontal line to its right labelled products, and a vertical arrow points downwards from the reactants line to the products line.

    Which row correctly describes the type of reaction and corresponding energy change?

    type of reaction

    energy change

    A

    endothermic

    heat is released

    B

    endothermic

    heat is absorbed

    C

    exothermic

    heat is released

    D

    exothermic

    heat is absorbed

      Choose your answer

      5
      1 mark

      Calcium and hydrochloric acid react to produce calcium chloride and hydrogen gas. The energy level diagram for the reaction is shown below.

      An energy level diagram. The vertical axis is labelled Energy. A horizontal line labelled Ca + 2HCl sits above a horizontal line to its right labelled CaCl2 + H2, and a vertical arrow points downwards from the upper line to the lower line.

      Which statement about this reaction is not correct?

      • The temperature of the surroundings increases.

      • The reaction is endothermic.

      • The products have less energy than the reactants.

      • Energy is released during the reaction.

      Choose your answer

      6
      1 mark

      The reaction pathway diagram for a reaction, with and without a catalyst, is shown.

      Energy vs progress diagram. Reactants at higher level than products. Two peaks: lower and higher. Different arrow displayed A = x axis to reactants. B = reactants to lower peak. C = x axis to products. D = reactants to higher peak.

      Which letter represents the activation energy of the catalysed reaction?

        Choose your answer

        1
        1 mark

        Which of the following processes is endothermic?

        • Reacting sodium with water.

        • The use of petrol in an engine.

        • Distilling crude oil.

        • Burning fossil fuels.

        Choose your answer

        2
        1 mark

        In all chemical reactions, bonds in the reactant species are broken and new bonds are formed in the products. Which statement is correct?

        • Bond breaking requires energy and is thus an exothermic process.

        • Bond breaking requires energy and is thus an endothermic process.

        • Bond breaking releases energy and is thus an exothermic process.

        • Bond breaking releases energy and is thus an endothermic process.

        Choose your answer

        3
        1 mark

        Which is true about chemical energy changes?

        Reaction type

        Energy flows

        Temperature of surroundings

        A

        exothermic

        to the surroundings

        increases

        B

        exothermic

        from the surroundings

        decreases

        C

        endothermic

        to the surroundings

        decreases

        D

        endothermic

        from the surroundings

        increases

          Choose your answer

          4
          1 mark

          The reaction profile for making nitrogen monoxide, NO, is shown below:

          A reaction pathway diagram. The vertical axis is labelled Energy and the horizontal axis progress of reaction. A horizontal line labelled N2 + O2 sits below a horizontal line to its right labelled 2NO, joined by a curve that rises to a peak above both of them. An upward arrow labelled 140 kJ runs from the level of the 2NO line to the peak, and an upward arrow labelled 180 kJ runs from the level of the N2 + O2 line to the 2NO line.

          What is the activation energy for this reaction?

          • +140 kJ

          • +180 kJ

          • +320 kJ

          • -330 kJ

          Choose your answer

          5
          1 mark

          Endothermic processes can be used in emergency sports injury treatment packs.

          What is true about these packs?

          • Absorb energy from the surroundings and transfer it to the injury

          • Can be re-used

          • Usually contain ammonium nitrate and water in separate compartments

          • Cause the temperature of the surroundings to increase

          Choose your answer

          6
          1 mark

          An endothermic reaction has an activation energy of x.

          Which reaction pathway diagram is correct for this reaction?

          q18-cie-o-level-chemistry-specimen-2023-paper-1

            Choose your answer

            7
            1 mark

            The formation of liquid water from hydrogen and oxygen may occur in three stages.

            1

            2H2(g) + O2(g) → 4H(g) + 2O(g)

            2

            4H(g) + 2O(g) → 2H2O(g)

            3

            2H2O(g) → 2H2O(l)

            Which stages are endothermic?

            • 1, 2 and 3

            • 1 only

            • 1 and 3

            • 2 only

            Choose your answer

            1
            1 mark

            Chlorine and ethane react together in an exothermic reaction to produce chloroethane and hydrogen chloride. The equation for the reaction is shown below.

            C2H6 + Cl2 → C2H5Cl + HCl

            The table below shows the relevant bond energies.

            bond

            bond energy / (kJ / mol)

            CーCl

            + 340

            CーC

            + 350

            CーH

            + 410

            ClーCl

            + 240

            HーCl

            + 430

            What is the energy change for the reaction between chlorine and ethane?

            • -120 kJ / mol

            • -1020 kJ / mol

            • +120 kJ / mol

            • +1020 kJ / mol

            Choose your answer

            2
            1 mark

            The production of ammonia involves the exothermic reaction between nitrogen and hydrogen. The equation for the reaction is shown.

            N2 + 3 H2 → 2 NH3

            The table shows the bond energies.

            bond

            bond energy / (kJ / mol)

            NーH

            +390

            HーH

            +436

            N☰N

            +945

            What is the energy released during the reaction?

            • -230 kJ / mol

            • -1025 kJ / mol

            • -87 kJ / mol

            • +87 kJ / mol

            Choose your answer

            3
            1 mark

            Chlorine and hydrogen react in an exothermic reaction producing hydrogen chloride. The equation for the reaction is shown.

            Cl2 + H2 → 2 HCl

            The table shows some of the bond energies involved. The total energy change for this reaction is -184 kJ / mol.

            bond

            bond energy / (kJ / mol)

            HーCl

            +430

            HーH

            +436

            ClーCl

            -

            What is the energy of the Cl─Cl bond?

            • -170 kJ / mol

            • +240 kJ / mol

            • +170 kJ / mol

            • -240 kJ / mol

            Choose your answer

            4
            1 mark

            Methane combusts in oxygen as shown producing an energy change of -890 kJ / mol.

            CH4 + 2O2 → CO2 + 2H2O

            The table shows some of the bond energies involved.

            bond

            bond energy / (kJ / mol)

            HーO

            +460

            O＝O

            +496

            CーH

            +410

            C＝O

            -

            What is the energy of the C＝O bond?

            • -155 kJ / mol

            • +333 kJ / mol

            • -840 kJ / mol

            • +841 kJ / mol

            Choose your answer

            5
            1 mark

            An energy level diagram is shown below.

            An energy level diagram. The vertical axis is labelled Energy and the horizontal axis Progress of reaction. A horizontal line on the left is joined by a curve that rises to a peak and then falls to a second horizontal line on the right, which lies above the first. An upward arrow labelled 1 runs from the level of the left-hand line towards the peak. An upward arrow labelled 2 runs from the level of the left-hand line to the right-hand line. The label 3 sits beside the right-hand line.

            Which row is correct for the points labelled 1, 2 and 3?

            1

            2

            3

            A

            activation energy

            energy change

            reactants

            B

            energy change

            activation energy

            products

            C

            energy change

            activation energy

            reactants

            D

            activation energy

            energy change

            products

              Choose your answer