Skip to main content
Back

Gibbs Free Energy quiz #1

Control buttons has been changed to "navigation" mode.
1/25

Terms in this set (25)

  • What is the value of ΔG when a system is at equilibrium?
    ΔG is zero at equilibrium.
  • What does the change in free energy of a reaction predict?
    The change in free energy predicts whether a reaction is spontaneous, non-spontaneous, or at equilibrium.
  • What does a positive value of ΔG indicate about a reaction?
    The reaction is non-spontaneous and favors reactants.
  • What determines the sign of ΔG for a reaction?
    The sign of ΔG is determined by the enthalpy (ΔH), entropy (ΔS), and temperature (T) of the reaction.
  • What is always positive when a spontaneous process occurs?
    The total entropy change of the universe (ΔS_universe) is always positive for a spontaneous process.
  • What are two good driving forces for spontaneity?
    A negative enthalpy change (ΔH < 0) and a positive entropy change (ΔS > 0) are good driving forces for spontaneity.
  • What is the free energy change calculated for?
    The free energy change is calculated to determine if a reaction is spontaneous, non-spontaneous, or at equilibrium.
  • What is the change in the free energy?
    The change in free energy (ΔG) is the difference in energy available to do work during a chemical reaction.
  • What is ΔG° for the reaction CaO(s) + CO₂(g) → CaCO₃(s)?
    ΔG° for the reaction can be calculated using standard free energies of formation for the reactants and products.
  • What is the value of ΔG at which a reaction becomes spontaneous? Express your answer numerically.
    A reaction becomes spontaneous when ΔG < 0.
  • What is ΔG° for the following reaction at 25 °C? CoBr₂(g) ⇌ CO(g) + Br₂(g), Kp = 4.11 × 10⁴
    ΔG° = –RT ln(Kp); substitute R = 8.314 J/mol·K, T = 298 K, and Kp = 4.11 × 10⁴ to calculate.
  • What is ΔG° for the following reaction at 25 °C? CO(g) + 2 H₂(g) ⇌ CH₃OH(g), K = 2.1 × 10⁻⁴
    ΔG° = –RT ln(K); substitute R = 8.314 J/mol·K, T = 298 K, and K = 2.1 × 10⁻⁴ to calculate.
  • What is ΔG° for the following reaction at 25 °C? CO(g) + 2 H₂(g) ⇌ CH₃OH(g), Kp = 2.1 × 10⁻⁴
    ΔG° = –RT ln(Kp); substitute R = 8.314 J/mol·K, T = 298 K, and Kp = 2.1 × 10⁻⁴ to calculate.
  • A chemical reaction that has a positive ΔG is correctly described as
    Non-spontaneous under the given conditions.
  • A chemical reaction that has a positive ΔG is best described as
    Non-spontaneous.
  • What is the value of the free energy change (ΔG) of a reaction at equilibrium?
    At equilibrium, ΔG is zero.
  • A chemical reaction that has a positive ΔG is best described as _____.
    Non-spontaneous.
  • If a chemical reaction has a negative ΔH and a negative ΔS, then
    The reaction is spontaneous only at low temperatures.
  • If ΔH < 0 and ΔS < 0, a reaction will be:
    Spontaneous at low temperatures.
  • If a chemical reaction has a positive ΔH and a positive ΔS, then
    The reaction is spontaneous only at high temperatures.
  • Determine ΔG° for a reaction when ΔG = –138.2 kJ/mol and Q = 0.043 at 298 K. (R = 8.314 J/mol·K)
    Use ΔG = ΔG° + RT ln(Q); solve for ΔG°.
  • Calculate the actual physiological ΔG for the reaction.
    Use ΔG = ΔG° + RT ln(Q), where Q reflects physiological concentrations.
  • Calculate the standard change in Gibbs free energy.
    Use ΔG° = ΔH° – TΔS° under standard conditions.
  • Use the data given here to calculate the values of ΔG_rxn at 25 °C.
    Apply ΔG_rxn = ΣΔG°_products – ΣΔG°_reactants using provided data.
  • If a chemical reaction has a positive ΔH and a negative ΔS, then
    The reaction is non-spontaneous at all temperatures.