Enthalpy of Fusion Formula: Explained with Examples

📚 Quick Study Guide

• 🧊 Enthalpy of Fusion Definition: The amount of heat required to change a substance from solid to liquid at its melting point at constant pressure.
• 🌡️ Formula: $\Delta H_{fus} = H_{liquid} - H_{solid}$ or $\Delta H_{fus} = q / n$, where $q$ is heat and $n$ is the number of moles.
• 📏 Units: Typically expressed in Joules per mole (J/mol) or Kilojoules per mole (kJ/mol).
• 📝 Key Point: Enthalpy of fusion is an endothermic process (heat is absorbed).

🧪 Practice Quiz

1. What does the enthalpy of fusion represent?
   1. A. The heat required to vaporize a substance.
   2. B. The heat required to melt a substance.
   3. C. The heat released when a substance freezes.
   4. D. The heat released when a substance condenses.
2. The enthalpy of fusion is typically measured in:
   1. A. Grams per mole (g/mol)
   2. B. Joules per Kelvin (J/K)
   3. C. Joules per mole (J/mol)
   4. D. Moles per liter (mol/L)
3. If 1000 J of heat are required to melt 0.1 moles of a substance, what is the enthalpy of fusion?
   1. A. 100 J/mol
   2. B. 1,000 J/mol
   3. C. 10,000 J/mol
   4. D. 0.0001 J/mol
4. Which of the following processes is associated with the enthalpy of fusion?
   1. A. Sublimation
   2. B. Deposition
   3. C. Melting
   4. D. Condensation
5. Is the enthalpy of fusion an endothermic or exothermic process?
   1. A. Endothermic
   2. B. Exothermic
   3. C. Neither
   4. D. Sometimes endothermic, sometimes exothermic
6. The enthalpy of fusion for water is approximately 6.01 kJ/mol. How much heat is needed to melt 0.5 moles of ice?
   1. A. 3.005 kJ
   2. B. 6.51 kJ
   3. C. 12.02 kJ
   4. D. 1.0 kJ
7. What happens to the temperature of a substance during the process of melting at its melting point?
   1. A. Increases
   2. B. Decreases
   3. C. Remains constant
   4. D. Fluctuates randomly