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Gas-Phase and Heterogeneous Equilibria: Flashcards

Revise Kp, converting between Kc and Kp, heterogeneous equilibria and ICE tables with pressures.

10 cardsIntermediate

10 cards

  1. Question
    What is Kp?
    Answer

    The equilibrium constant written with partial pressures of gases (in atm) instead of concentrations.

  2. Question
    Write Kp for N₂ + 3H₂ ⇌ 2NH₃.
    Answer

    Kp=(PNHX3)2PNX2(PHX2)3K_\text{p} = \dfrac{(P_{\ce{NH3}})^2}{P_{\ce{N2}}(P_{\ce{H2}})^3}

  3. Question
    Give the equation linking Kp and Kc.
    Answer

    Kp=Kc(RT)ΔnK_\text{p} = K_\text{c}(RT)^{\Delta n}, with R = 0.08206 L·atm/(mol·K) and T in K.

  4. Question
    What is Δn in Kp = Kc(RT)^Δn?
    Answer

    Moles of gaseous products − moles of gaseous reactants.

  5. Question
    When is Kp equal to Kc?
    Answer

    When Δn = 0 (same number of gas moles on both sides), e.g. H₂ + I₂ ⇌ 2HI.

  6. Question
    What is a heterogeneous equilibrium?
    Answer

    An equilibrium involving substances in more than one phase.

  7. Question
    Which substances are left out of K expressions?
    Answer

    Pure solids and pure liquids.

  8. Question
    Write Kp for CaCO₃(s) ⇌ CaO(s) + CO₂(g).
    Answer

    Kp = P(CO₂)

  9. Question
    P(N₂O₄) = 0.70 atm, P(NO₂) = 0.32 atm at equilibrium. Find Kp for N₂O₄ ⇌ 2NO₂.
    Answer

    Kp = (0.32)² ÷ 0.70 = 0.15

  10. Question
    For C(s) + H₂O(g) ⇌ CO(g) + H₂(g), what is Δn?
    Answer

    +1 (2 gas moles − 1 gas mole; the solid is not counted).