Thermodynamics and Gibbs Free Energy
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Questions and Answers

Which equation correctly represents the change in Gibbs free energy during a spontaneous process?

  • $ΔG = ΔH + TΔS$
  • $ΔG < 0$ (correct)
  • $ΔG > 0$
  • $ΔG = ΔH - TΔS$ (correct)

    • What is true about the entropy of a perfect crystalline substance at absolute zero (0 K)?

  • The entropy is equal to one unit.
  • The entropy is zero. (correct)
  • The entropy increases.
  • The entropy is undefined.

    • How is the entropy change of the surroundings (ΔSsurr) calculated?

  • $ΔSsurr = rac{T}{ΔH_{sys}}$
  • $ΔSsurr = T imes ΔH_{sys}$
  • $ΔSsurr = rac{ΔH_{sys}}{T}$ (correct)
  • $ΔSsurr = rac{ΔH_{sys}}{T^2}$

    • Which statement accurately describes the relationship between ΔG and the equilibrium constant K?

    <p>$ΔG = -RTlnK$</p> Signup and view all the answers

    In the context of biochemical reactions, what role does ATP hydrolysis typically play?

    <p>It drives non-spontaneous reactions.</p> Signup and view all the answers

    Study Notes

    Entropy

    • Definition: A measure of disorder or randomness in a system.
    • Equation: ΔS = ∑Sproducts − ∑Sreactants
    • Second Law of Thermodynamics: In any spontaneous process, the entropy of the universe increases.
    • Third Law of Thermodynamics: The entropy of a perfect crystalline substance is zero at absolute zero (0 K).

    Spontaneous Processes

    • Criteria for Spontaneity: A process is spontaneous if it leads to an increase in the entropy of the universe.
    • Free Energy (G): Combines enthalpy (H) and entropy (S) to predict spontaneity.
    • Equation: ΔG = ΔH – TΔS
    • Where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, and T is the temperature in Kelvin.

    Gibbs Free Energy (ΔG)

    • Spontaneity:
    • ΔG < 0: Spontaneous process.
    • ΔG > 0: Non-spontaneous process.
    • ΔG = 0: Equilibrium.
    • Standard Free Energy Change (ΔG°):
    • ΔG° = ∑ΔG°(products) − ∑ΔG°(reactants)
    • Relationship to Equilibrium Constant (K):
    • ΔG° = −RTlnK
    • Where R is the gas constant (8.314 J/mol·K) and T is the temperature in Kelvin.

    Equilibrium

    • At Equilibrium: ΔG = 0
    • The forward and reverse reactions occur at the same rate.

    Entropy Changes in Reactions

    • Entropy Change of the System (ΔSsys):
    • ΔSsys = ∑Sproducts − ∑Sreactants
    • Entropy Change of the Surroundings (ΔSsurr):
    • ΔSsurr = −ΔHsys/T
    • Where ΔHsys is the enthalpy change of the system and T is the temperature in Kelvin.

    Biological Reactions

    • Biological Reactions: Often driven by ATP hydrolysis.
    • Coupled Reactions: Non-spontaneous reactions can be driven by coupling them with spontaneous ones.
    • Equation for Coupled Reactions:*
    • ΔGtotal = ΔG1 + ΔG2

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    Description

    This quiz covers key concepts in thermodynamics, including entropy, spontaneity, and Gibbs free energy. You will explore the definitions, equations, and laws governing these phenomena. Test your knowledge and understanding of these fundamental principles crucial in chemistry and physics.

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