GCSEChemistryOCR GatewayExam Questions3. Chemical Reactions3.2 Energetics

 Energetics (OCR Gateway GCSE Chemistry)

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3.2 Energetics

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3.2 Energetics

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11 mark

What is meant by the activation energy in a chemical reaction?

  • The total energy used up when a reaction has stopped.

  • The energy absorbed during a reaction.

  • The energy released during a reaction.

  • The minimum energy needed for a reaction to occur.

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21 mark

What is the activation energy for a reaction?

  • The difference between the energy of the reactants and the products

  • The energy needed for a reaction to start

  • The energy of the reactants

  • The energy of the products

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11 mark

Which statement describes activation energy?

  • The energy level of the reactants

  • The energy level of the products

  • The energy needed to break the bonds in the reactants

  • The difference in energy level between the reactants and products

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2
Sme Calculator1 mark

Chlorine reacts with methane in sunlight.

 CH4 + Cl2  → CH3Cl + HCl

The diagram below shows the displayed formulae for the reaction of chlorine with methane.

3-2-q2-ocr-gcse-mcq- 

The table below shows the bond energies and the overall energy change in the reaction. 

  C-H Cl-Cl C-Cl H-Cl Overall energy change
Energy in kJ/mol 413 243 X 432 -122

What is the value of X?

  • 67 kJ

  • 134 kJ

  • 346 kJ

  • 542 kJ

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3
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How much energy is needed to break all the bonds in 0.025 g of nitrogen gas?

The relative atomic mass, Ar, of N is 14.

Bond  Bond energy in kJ/mol
Nidentical toN  945

  • 1701 J

  • 1701 kJ

  • 844 J

  • 844 kJ

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41 mark

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

 3-2-q4-ocr-gcse-mcq

What does the label X represent?

  • Activation energy

  • Overall energy change

  • Reactants

  • Progress of the reaction

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51 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

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    6
    Sme Calculator    1 mark

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

    3-2-q6-ocr-gcse-mcq-

     

    What is the activation energy for this reaction?

    • +140 kJ

    • +180 kJ

    • +320 kJ

    • -330 kJ

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    71 mark

    Which statement is true about exothermic and endothermic reactions?

    • The products have more energy than the reactants in an exothermic reaction

    • The products have more energy than the reactants in an endothermic reaction

    • The activation energy for an exothermic reaction is always larger than the activation energy for an endothermic reaction

    • Most reactions are endothermic

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    81 mark

    Look at the energy changes in the reaction profile for the reaction between hydrogen and chlorine

    q12-paper-1-specimen-2016-ocr-gcse-chemistry

    Which energy change shows the overall energy change of the reaction?

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