AP Chemistry Questions on Thermodynamics and Equilibrium

📚 Quick Study Guide

• 🔥 Thermodynamics: Deals with energy transfer and transformations.
• 🌡️ Enthalpy ($\Delta H$): Heat absorbed or released in a reaction at constant pressure. $\Delta H < 0$ is exothermic; $\Delta H > 0$ is endothermic.
• entropydelta Entropy ($\Delta S$): Measure of disorder or randomness. Increases with increasing temperature, volume, or number of particles.
• ⚙️ Gibbs Free Energy ($\Delta G$): Predicts spontaneity of a reaction. $\Delta G = \Delta H - T\Delta S$. $\Delta G < 0$ is spontaneous.
• ⚖️ Equilibrium: State where the rates of forward and reverse reactions are equal.
• 📈 Equilibrium Constant (K): Ratio of products to reactants at equilibrium. $K = \frac{[Products]}{[Reactants]}$.
• ⚠️ Le Chatelier's Principle: If a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.

🧪 Practice Quiz

1. Which of the following conditions indicates a spontaneous reaction at all temperatures?
   1. A. $\Delta H > 0$, $\Delta S > 0$
   2. B. $\Delta H < 0$, $\Delta S < 0$
   3. C. $\Delta H < 0$, $\Delta S > 0$
   4. D. $\Delta H > 0$, $\Delta S < 0$
2. For the reaction $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$, what is the effect of increasing the pressure?
   1. A. Shifts equilibrium to the right
   2. B. Shifts equilibrium to the left
   3. C. No effect on the equilibrium
   4. D. Increases the value of K
3. Which of the following processes leads to an increase in entropy?
   1. A. Freezing of water
   2. B. Condensation of steam
   3. C. Dissolving sugar in water
   4. D. Formation of a crystal
4. What is the value of $\Delta G$ at equilibrium?
   1. A. Positive
   2. B. Negative
   3. C. Zero
   4. D. Depends on temperature
5. The equilibrium constant, K, for a reaction is 100 at 298 K. What does this indicate about the reaction?
   1. A. The reaction is very slow
   2. B. The reaction is exothermic
   3. C. The products are favored at equilibrium
   4. D. The reactants are favored at equilibrium
6. According to Le Chatelier's principle, adding heat to an endothermic reaction at equilibrium will:
   1. A. Shift the equilibrium towards reactants
   2. B. Shift the equilibrium towards products
   3. C. Have no effect on the equilibrium
   4. D. Decrease the value of K
7. Which of the following statements is always true for a spontaneous process?
   1. A. $\Delta H$ is negative
   2. B. $\Delta S$ is negative
   3. C. $\Delta G$ is negative
   4. D. $\Delta G$ is positive