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Integrated Rate Laws and Mechanisms: Flashcards

Revise zero-, first- and second-order integrated rate laws, straight-line plots, half-lives and reaction mechanisms.

10 cardsAdvanced

10 cards

  1. Question
    Zero-order integrated rate law and straight-line plot?
    Answer

    [A] = [A]₀ − kt; [A] against t is a straight line with slope −k.

  2. Question
    First-order integrated rate law and straight-line plot?
    Answer

    ln[A] = ln[A]₀ − kt; ln[A] against t is a straight line with slope −k.

  3. Question
    Second-order integrated rate law and straight-line plot?
    Answer

    1/[A] = 1/[A]₀ + kt; 1/[A] against t is a straight line with slope +k.

  4. Question
    Half-life for each order?
    Answer

    Zero: [A]₀/2k. First: ln 2/k (constant). Second: 1/(k[A]₀).

  5. Question
    How can you recognize first order from data?
    Answer

    Equal time intervals give equal fractions remaining, and the half-life is constant; ln[A] against t is straight.

  6. Question
    What happens to successive second-order half-lives?
    Answer

    Each is twice as long as the one before, because [A]₀ halves each time.

  7. Question
    What is an elementary step?
    Answer

    A single step in a mechanism; its rate law follows directly from the particles that collide.

  8. Question
    What is the rate-determining step?
    Answer

    The slowest step in a mechanism; it sets the overall rate.

  9. Question
    What is an intermediate?
    Answer

    A species formed in one step and used up in a later step; it does not appear in the overall equation.

  10. Question
    Two conditions for a valid mechanism?
    Answer

    The steps add up to the overall equation, and the predicted rate law matches the experimental one.