5.3.3 Gibbs free energy

• The Gibbs Free Energy is calculated using the formula: ΔG = ΔH - TΔS
• Match the variable with its symbol and units:

  Enthalpy ↔️ H, kJ mol⁻¹

  Temperature ↔️ T, K

  Entropy ↔️ S, J mol⁻¹ K⁻¹

  Gibbs Free Energy ↔️ G, kJ mol⁻¹
• In the ΔG formula, ΔH represents the enthalpy change
• Match the variable with its symbol and effect on spontaneity:

  Enthalpy Change (ΔH) ↔️ Negative favors, positive disfavors

  Temperature (T) ↔️ Affects the TΔS term

  Entropy Change (ΔS) ↔️ Positive favors, negative disfavors

  Gibbs Free Energy Change (ΔG) ↔️ Negative indicates spontaneity
• Negative values of ΔH favor spontaneity in a reaction.


  True
• What is entropy (ΔS) a measure of?

  Disorder or randomness
• A positive ΔS indicates an increase in disorder, which generally favors spontaneity.


  True
• A negative ΔS indicates a decrease in disorder
• The Gibbs Free Energy formula is G = H - TS.


  True
• Match the ΔG value with its corresponding spontaneity:

  ΔG < 0 ↔️ Spontaneous

  ΔG = 0 ↔️ Equilibrium

  ΔG > 0 ↔️ Non-spontaneous
• A positive ΔS always leads to a spontaneous reaction.

  False
• What is enthalpy (ΔH) measured in?

  kJ/mol
• A positive ΔS means the system's disorder increases, favoring spontaneity.


  True
• Higher temperatures can favor reactions with positive ΔS, while lower temperatures favor reactions with negative ΔH.
• Match the ΔG scenario with its example:

  ΔG < 0 ↔️ Combustion of methane

  ΔG = 0 ↔️ Phase transition at melting point

  ΔG > 0 ↔️ Photosynthesis without light
• A negative ΔG indicates a spontaneous reaction.


  True
• What does a ΔG of zero indicate about a reaction?

  Reaction is at equilibrium
• Gibbs Free Energy predicts spontaneity at constant temperature and pressure.


  True
• A negative ΔG indicates a spontaneous reaction.
• What does the ΔH term in the Gibbs Free Energy formula represent?

  Enthalpy change
• Positive ΔS values favor spontaneity.


  True
• If ΔH = -50 kJ/mol and ΔS = 0.1 kJ/(mol·K) at T = 300 K, then ΔG = -80 kJ/mol
• What does a negative ΔG indicate about a reaction?

  The reaction is spontaneous
• What is the effect of a negative ΔH on the spontaneity of a reaction?

  It favors spontaneity
• What is entropy (ΔS) a measure of?

  Disorder or randomness
• A positive ΔS generally favors spontaneity.


  True
• At higher temperatures, the term `-TΔS` becomes more significant, especially if ΔS is positive
• A reaction with ΔG < 0 is spontaneous.


  True
• The Gibbs Free Energy (ΔG) and the equilibrium constant (K) are related by the formula: ΔG = -RTlnK
• What is the value of the ideal gas constant (R) in the Gibbs Free Energy equation?

  8.314 J/(mol·K)
• The ideal gas constant (R) has a value of 8.314
• What is the unit of the equilibrium constant (K)?

  Unitless
• What is the formula for Gibbs Free Energy involving enthalpy (ΔH) and entropy (ΔS)?

  ΔG = ΔH - TΔS
• If ΔG is equal to zero, the reaction is at equilibrium
• What is the ΔG for a reaction with ΔH = -50 kJ/mol, ΔS = 0.1 kJ/(mol·K), and T = 300 K?

  -80 kJ/mol
• What does a higher temperature do to the effect of entropy change (ΔS) on spontaneity?

  Amplifies it
• A negative ΔG indicates a spontaneous process.

  True
• Arrange the conditions that favor a spontaneous reaction according to ΔG:

  1️⃣ Exothermic reactions (negative ΔH)

  2️⃣ Reactions with a positive ΔS

  3️⃣ Lower temperatures favoring negative ΔH
• Exothermic reactions with a negative ΔH are more likely to be spontaneous.


  True
• A negative ΔH indicates that the reaction is exothermic