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Chemical Equilibrium: Flashcards

Revise dynamic equilibrium, Kc expressions, Q versus K and ICE tables.

10 cardsIntermediate

10 cards

  1. Question
    What is dynamic equilibrium?
    Answer

    The state in which the forward and reverse reactions continue at equal rates, so concentrations stay constant.

  2. Question
    Are reactant and product concentrations equal at equilibrium?
    Answer

    No. They are constant, not equal.

  3. Question
    Write KcK_\text{c} for NX2+3 HX2⇌2 NHX3\ce{N2 + 3H2 <=> 2NH3}.
    Answer

    Kc=[NHX3]2[NX2][HX2]3K_\text{c} = \dfrac{[\ce{NH3}]^2}{[\ce{N2}][\ce{H2}]^3}

  4. Question
    Which substances are left out of KcK_\text{c}?
    Answer

    Pure solids and pure liquids (including water as the solvent).

  5. Question
    What does a very large KcK_\text{c} mean?
    Answer

    At equilibrium the mixture is mostly products: the reaction goes almost to completion.

  6. Question
    If Q<KQ < K, which way does the reaction go?
    Answer

    Forward (→), making more products until Q=KQ = K.

  7. Question
    If K for a reaction is 800, what is K for the reverse reaction?
    Answer

    1800=1.25×10−3\dfrac{1}{800} = 1.25 \times 10^{-3}

  8. Question
    What is the only factor that changes the value of KcK_\text{c}?
    Answer

    Temperature.

  9. Question
    What do the letters in an ICE table stand for?
    Answer

    Initial, Change, Equilibrium (concentrations, in M).

  10. Question
    Why does KcK_\text{c} have no unit?
    Answer

    Each concentration is divided by the standard concentration c°=1 Mc° = 1\ \text{M}, so the units cancel.