Spontaneity in Chemistry: Examples and Applications

📚 Quick Study Guide

• 🔥 Spontaneous Processes: Reactions that occur without continuous external assistance.
• 🌡️ Enthalpy ($\Delta H$): A measure of the heat absorbed or released in a reaction. Exothermic reactions ($\Delta H < 0$) tend to be spontaneous.
• 🌪️ Entropy ($\Delta S$): A measure of disorder or randomness. Reactions that increase entropy ($\Delta S > 0$) tend to be spontaneous.
• ⚙️ Gibbs Free Energy ($\Delta G$): Determines spontaneity at a given temperature and pressure: $\Delta G = \Delta H - T\Delta S$.
• ✅ Spontaneity Criteria:
  • $\Delta G < 0$: Spontaneous
  • $\Delta G > 0$: Non-spontaneous
  • $\Delta G = 0$: Equilibrium
• 🔢 Temperature Dependence: The spontaneity of some reactions depends on temperature due to the $T\Delta S$ term in the Gibbs Free Energy equation.

🧪 Practice Quiz

1. Which of the following conditions indicates a spontaneous reaction?
   1. $\Delta G > 0$
   2. $\Delta H > 0$ and $\Delta S < 0$
   3. $\Delta G < 0$
   4. $\Delta H < 0$ and $\Delta S < 0$
2. What is the term for the measure of disorder in a system?
   1. Enthalpy
   2. Entropy
   3. Gibbs Free Energy
   4. Heat Capacity
3. For a reaction to be spontaneous at all temperatures, which condition must be met?
   1. $\Delta H > 0$ and $\Delta S > 0$
   2. $\Delta H < 0$ and $\Delta S < 0$
   3. $\Delta H < 0$ and $\Delta S > 0$
   4. $\Delta H > 0$ and $\Delta S < 0$
4. Which of the following processes is most likely to be spontaneous?
   1. Ice forming at room temperature
   2. Water freezing at -10°C
   3. Boiling water at 90°C
   4. Iron rusting in a vacuum
5. What does a negative value of $\Delta H$ usually indicate?
   1. An endothermic reaction
   2. An increase in entropy
   3. A decrease in entropy
   4. An exothermic reaction
6. If $\Delta H$ is positive and $\Delta S$ is positive, the reaction will be spontaneous at:
   1. Low temperatures
   2. All temperatures
   3. High temperatures
   4. No temperatures
7. Which of the following is NOT a state function?
   1. Enthalpy
   2. Entropy
   3. Gibbs Free Energy
   4. Work