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Chapter 5 – Practice Problems (Phase Transitions – Melting, Boiling, and Subliming)

  1. What is the difference between melting and solidification?
  2. What is the difference between boiling and condensation?
  3. Describe the molecular changes when a solid becomes a liquid.
  4. Describe the molecular changes when a liquid becomes a gas.
  5. What is the energy change when 78.0 g of Hg melt at −38.8°C?
  6. What is the energy change when 30.8 g of Al solidify at 660°C?
  7. What is the energy change when 111 g of Br2 boil at 59.5°C?
  8. What is the energy change when 98.6 g of H2O condense at 100°C?
  9. Each of the following statements is incorrect. Rewrite them so they are correct.
    • Temperature changes during a phase change.
    • The process of a liquid becoming a gas is called sublimation.
  10. Each of the following statements is incorrect. Rewrite them so they are correct.
    • The volume of a gas contains only about 10% matter, with the rest being empty space.
    • ΔHsub is equal to ΔHvap.
  11. Write the chemical equation for the melting of elemental sodium.
  12. Write the chemical equation for the solidification of benzene (C6H6).
  13. Write the chemical equation for the sublimation of CO2.
  14. Write the chemical equation for the boiling of propanol (C3H7OH).
  15. What is the ΔHsub of H2O?
  16. The ΔHsub of I2 is 60.46 kJ/mol, while its ΔHvap is 41.71 kJ/mol. What is the ΔHfus of I2?

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