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Chemistry: Thermodynamics & Thermochemistry Flashcards

7 cards from real AP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which process always has a positive ΔS for the system?

    Answer: Sublimation of solid CO₂

    Sublimation goes from solid to gas, greatly increasing disorder and entropy.

  2. For an exothermic reaction with a decrease in entropy, the reaction is spontaneous at what temperatures?

    Answer: Low temperatures

    When ΔH < 0 and ΔS < 0, ΔG is negative only at low temperatures.

  3. What is the first law of thermodynamics?

    Answer: Energy is conserved

    The first law states energy cannot be created or destroyed, only transferred or converted.

  4. The internal energy change ΔU equals which expression?

    Answer: q + w

    ΔU = q + w, where heat added and work done on the system increase internal energy.

  5. A reaction has ΔH = +50 kJ and ΔS = +150 J/K. At what approximate temperature does it become spontaneous?

    Answer: Above 333 K

    Setting ΔG = 0, T = ΔH/ΔS = 50000/150 ≈ 333 K, spontaneous above this.

  6. What does a calorimeter measure?

    Answer: Heat transferred in a process

    A calorimeter measures the heat absorbed or released during a physical or chemical process.

  7. Bond breaking is what type of process energetically?

    Answer: Endothermic

    Breaking bonds requires energy input, making it endothermic.