Free Energy and Equilibrium - AP Chemistry

1. Determine the sign of $\triangle G$ for a process at equilibrium.

   $\triangle G = 0$. At equilibrium, there is no net change in free energy.

2. Which term describes a reaction with $\triangle H > 0$?

   Endothermic. Positive enthalpy change indicates heat is absorbed from surroundings.

3. What is the effect of increasing temperature on an endothermic reaction's equilibrium position?

   Shifts to the right (toward products). Higher temperature favors the endothermic direction according to Le Châtelier's principle.

4. What happens to the equilibrium constant $K$ as temperature increases for an exothermic reaction?

   $K$ decreases. Higher temperature disfavors exothermic reactions, reducing $K$.

5. What condition is necessary for a reaction to be at equilibrium in terms of $Q$ and $K$?

   $Q = K$. At equilibrium, the reaction quotient equals the equilibrium constant.

6. State the equation relating Gibbs free energy and reaction quotient $Q$.

   $\triangle G = \triangle G^\text{°} + RT \text{ln}Q$. This equation relates free energy to reaction progress via quotient $Q$.

7. What is the effect of increasing volume on the equilibrium of a gaseous reaction?

   Shifts toward more moles of gas. Larger volume favors the side with more gas molecules.

8. What is the effect of increasing temperature on an exothermic reaction's equilibrium position?

   Shifts to the left (toward reactants). Higher temperature opposes the exothermic direction per Le Châtelier's principle.

9. Which term describes a reaction with $\triangle H > 0$?

   Endothermic. Positive enthalpy change indicates heat is absorbed from surroundings.

10. What is the term for the energy required to break bonds in reactants?

    Bond dissociation energy. Energy input needed to break existing chemical bonds in reactants.

11. What is the meaning of Gibbs free energy being state function?

    Depends only on initial and final states. State functions are path-independent, only depending on endpoints.

12. What is the significance of $\triangle G = 0$?

    The system is at equilibrium. At equilibrium, forward and reverse reaction rates are equal.

13. What does the term 'entropy' refer to in thermodynamics?

    The measure of disorder or randomness. Entropy quantifies the number of possible microstates in a system.

14. What does the term 'enthalpy' refer to in thermodynamics?

    The total heat content of a system. Enthalpy represents the total energy stored in chemical bonds.

15. Identify the units for Gibbs free energy change, $\triangle G$.

    Joules (J). Energy units match the dimensions of enthalpy and entropy terms.

16. What is the significance of the equilibrium constant $K$ being less than 1?

    Reactants are favored at equilibrium. Small $K$ values indicate equilibrium lies toward the reactant side.

17. What is the effect of a common ion on the solubility of a salt?

    Decreases solubility. Common ion effect shifts equilibrium by Le Châtelier's principle.

18. Which term describes a reaction with $\triangle H > 0$?

    Endothermic. Positive enthalpy change indicates heat is absorbed from surroundings.

19. What does a negative $\triangle G$ indicate about a reaction?

    The reaction is spontaneous. Negative $\triangle G$ means the process proceeds forward without external energy.

20. What is the value of $R$ in the equation $\triangle G = -RT \text{ln}K$?

    $8.314 \text{ J/mol·K}$. Universal gas constant used in thermodynamic calculations.

21. What is the effect of increasing pressure on the equilibrium of a gaseous reaction?

    Shifts toward fewer moles of gas. Higher pressure favors the side with fewer gas molecules.

22. What happens to the equilibrium constant $K$ as temperature increases for an endothermic reaction?

    $K$ increases. Higher temperature favors endothermic reactions, increasing $K$.

23. What is the relationship between Gibbs free energy and reaction spontaneity?

    Negative $\triangle G$ indicates spontaneity. The sign of $\triangle G$ determines if a reaction proceeds spontaneously.

24. What is the effect of adding a catalyst on the equilibrium position?

    No effect on equilibrium position. Catalysts speed up both forward and reverse reactions equally.

25. What does a positive $\triangle G$ indicate about a reaction?

    The reaction is non-spontaneous. Positive $\triangle G$ means external energy is required for the process to occur.

26. Which thermodynamic quantity is directly related to the spontaneity of a process?

    Gibbs free energy, $\triangle G$. Gibbs free energy determines whether reactions proceed spontaneously.

27. How does the addition of an inert gas at constant volume affect equilibrium?

    No effect on equilibrium. Inert gases don't participate and don't change partial pressures.

28. Which term describes a reaction with $\triangle H < 0$?

    Exothermic. Negative enthalpy change indicates heat is released to surroundings.

29. State the relationship between $\triangle G^\text{°}$ and $K$ for a reaction at equilibrium.

    $\triangle G^\text{°} = -RT \text{ln}K$. Standard free energy change relates directly to equilibrium constant.

30. Identify the units commonly used for entropy, $S$.

    Joules per Kelvin (J/K). Entropy has units of energy per temperature unit.

31. What is the significance of the equilibrium constant $K$ being greater than 1?

    Products are favored at equilibrium. Large $K$ values indicate equilibrium lies toward the product side.

32. What does Le Châtelier's principle predict?

    How a system at equilibrium responds to changes. Le Châtelier's principle describes equilibrium shifts to counteract disturbances.

33. Identify the condition under which a reaction is at dynamic equilibrium.

    Rate of forward and reverse reactions are equal. Dynamic equilibrium means constant concentrations with ongoing reactions.

34. What is the effect of decreasing temperature on an exothermic reaction's equilibrium position?

    Shifts to the right (toward products). Lower temperature favors the exothermic direction per Le Châtelier's principle.

35. State the equation relating $\triangle G$ and equilibrium constant $K$.

    $\triangle G = -RT \text{ln}K$. This equation connects thermodynamics ($\triangle G$) to kinetics ($K$).

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