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Enthalpy and Calorimetry: Flashcards

Revise exothermic and endothermic reactions, ΔH, specific heat capacity, q = mcΔT and calorimetry.

10 cardsIntermediate

10 cards

  1. Question
    What is an exothermic reaction?
    Answer

    A reaction that releases heat to the surroundings; ΔH is negative.

  2. Question
    What is an endothermic reaction?
    Answer

    A reaction that absorbs heat from the surroundings; ΔH is positive.

  3. Question
    Define ΔH.
    Answer

    The enthalpy change: the heat change at constant pressure, ΔH = H(products) − H(reactants).

  4. Question
    Write the equation for the heat gained or lost by a substance.
    Answer

    q=m×c×ΔTq = m \times c \times \Delta T

  5. Question
    What is the specific heat capacity of water?
    Answer

    4.184 J/(g·°C), the same as 4.184 J/(g·K)

  6. Question
    Heat needed to warm 250. g of water by 60.0 °C?
    Answer

    (250. g)(4.184 J/(g·°C))(60.0 °C) = 6.28 × 10⁴ J = 62.8 kJ

  7. Question
    In calorimetry, how is q(reaction) related to q(solution)?
    Answer

    q(reaction) = −q(solution): heat lost by one is gained by the other.

  8. Question
    The solution in a calorimeter warms up. Is the reaction exothermic or endothermic?
    Answer

    Exothermic (ΔH negative): the reaction released heat to the solution.

  9. Question
    CH₄ + 2O₂ → CO₂ + 2H₂O has ΔH = −890.5 kJ. What is ΔH for the reverse reaction?
    Answer

    +890.5 kJ (reversing changes the sign)

  10. Question
    Why is ΔT the same in °C and in K?
    Answer

    A degree Celsius and a kelvin are the same size; only the zero points differ.