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Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter

Energetics

117 practice questions

Start practising (51 questions)

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Practice questions

51–51 of 51 · Easy

  1. Question 51

    5 marks · Easy

    Magnesium reacts with dilute hydrochloric acid in a reaction described below:

    The reaction is exothermic. An energy profile for this reaction is shown below, but the axes and key features have not been labelled.

    (a)
    Geometry diagram with points Reactants, Products, AReactantsProducts
    Incomplete energy profile diagram for: \ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)}
    (i)

    On the diagram, clearly label: - the correct position of the reactants and products; - the activation energy; - the enthalpy change (ΔH), with an arrow showing its direction.

    [2 marks]
    (b)

    In a second experiment, a student dissolves ammonium chloride (NH₄Cl) in water. She uses 50.0 g of water at 24.0°C. After the salt dissolves, the final temperature is 19.7°C. The specific heat capacity, c, of water is 4.18 J/(g°C).

    Calculate the heat energy change (Q) for the dissolving process. State if the reaction is exothermic or endothermic, and explain your answer.

    (i)

    Calculate the heat energy change, Q, for this process. Give the unit.

    [2 marks]
    (ii)

    State if this process is exothermic or endothermic and explain your answer.

    [1 mark]
    Answer and see the solution →