when do you use 0= delta G naught + RTlnK? I know how to use the equation to find K, but when is the equation above used?

Gibbs Free Energy and Equilibrium

(using text Chemistry the Central Science)

2 Answers

  • 11 months ago
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    Gibbs free energy ....

    The Gibbs free energy expression for non-standard conditions

    ΔG = ΔG° + RTlnQ ........... Q is the reaction quotient(*)

    If a system is at equilibrium, then ΔG = 0 an Q = K

    0 = ΔG° + RTlnK

    ΔG° = -RTlnK

    * The expression for the reaction quotient looks just like the equilibrium expression, but does not include equilibrium concentrations. Q might be based on the initial concentrations

  • 11 months ago

    ΔG° = Standard Gibb's free energy (in J mol⁻¹)

    R = Gas constant = 8.314 J mol⁻¹ K⁻¹

    T = Temperature (in K)

    K = equilibrium constant

    The expression 0 = ΔG° + R T ln(K) can be used in 2 cases:

    Case 1: Rearrange to ΔG° = R T ln(K)

    Calculate the standard Gibb's free energy, ΔG°, at a certain temperature when the equilibrium constant, K, is known.

    Case 2: Rearrange to ln(K) = ΔG° / (R T)

    Calculate the equilibrium constant, K, at a certain temperature when the standard Gibb's free energy, ΔG°, is known.

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