15.1 Equilibrium and Equilibrium Constants

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    The rate of the forward reaction equals the rate of the reverse reaction.
    Concentrations of reactants and products are not changing.

    Equilibrium Constants (Law of Mass Action)

    -Equals the ratio of the concentrations of products to the concentrations of reactants at equilibrium raised to the power of their coefficients.
    -Only aqueous and gaseous species are included.
    -Equilibrium constants are CONSTANTS; the value will only change with a change in temperature.
    -An equilibrium constant also equals the ratio of the forward and reverse rate constants.

    K >> 1 Favors Products
    K << 1 Favors Reactants
    10-3 < K < 103 Reactants and products
    both present at equilibrium
    equilibrium constant 01

    2C(s) + O2(g) ⇌ 2CO(g)
    Write the equilibrium constant expression (Kc and Kp) for the reaction above.

    Kp vs Kc

    Kp = Kc (RT)Δn          Δn = change in moles gas          R = 0.0821 L•atm/mol•K

    If for 2C(s) + O2(g) ⇌ 2CO(g) Kc = 1200 at 400K, then what is the value of Kp?

    2SO2(g) + O2(g) ⇌ 2SO3(g)      Kc = 4.0

    Based on the reaction above, what are the equilibrium constants for the following reactions?

    2SO3(g) ⇌ 2SO2(g) + O2(g)

    SO2(g) + ½O2(g) ⇌ SO3(g)

    SO3(g) ⇌ SO2(g) + ½O2(g)