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Gibbs Free Energy quiz #1 Flashcards

Gibbs Free Energy quiz #1
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  • What does it mean when the Gibbs free energy change (ΔG) of a reaction is zero, and how does this relate to equilibrium?
    When ΔG is zero, the reaction is at equilibrium, meaning there is no net change in the concentrations of reactants and products, and no work can be done by the system.
  • How can the direction of a chemical reaction be predicted using the reaction quotient (Q) and the equilibrium constant (K)?
    If Q < K, the reaction proceeds forward to form more products; if Q > K, the reaction proceeds in reverse to form more reactants; if Q = K, the reaction is at equilibrium.
  • What does it mean when the Gibbs free energy change (ΔG) of a reaction is zero?
    When ΔG is zero, the reaction is at equilibrium, meaning there is no net change in the concentrations of reactants and products, and no work can be done by the system.
  • How can the direction of a chemical reaction be predicted using the reaction quotient (Q) and the equilibrium constant (K)?
    If Q < K, the reaction proceeds forward to form more products; if Q > K, the reaction proceeds in reverse to form more reactants; if Q = K, the reaction is at equilibrium.
  • What is the standard Gibbs free energy equation under standard conditions?
    The standard Gibbs free energy change (ΔG°) is calculated as ΔG° = −R·T·ln(K), where R is the gas constant, T is temperature in Kelvin, and K is the equilibrium constant.
  • How do standard conditions differ from physiological conditions in the context of Gibbs free energy?
    Standard conditions are defined as 25°C (298 K), 1 atm pressure, and 1 M concentrations, while physiological conditions can vary and often do not match these values.
  • Why are most cellular reactions not at equilibrium?
    Cellular reactions are rarely at equilibrium because reactants and products are constantly being added or removed, and conditions within cells are always changing.
  • How is the actual Gibbs free energy change (ΔG) under physiological conditions calculated?
    The actual ΔG is calculated using the equation ΔG = ΔG° + R·T·ln(Q), where Q is the reaction quotient reflecting current concentrations.
  • What does a positive value of ΔG under standard conditions indicate about a reaction?
    A positive ΔG under standard conditions means the reaction is endergonic and non-spontaneous under those conditions.
  • How can a reaction that is non-spontaneous under standard conditions become spontaneous in a cell?
    A reaction can become spontaneous in a cell if the actual concentrations of reactants and products (Q) make ΔG negative, even if ΔG° is positive.