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Thermodynamics: Review Questions for AP Chemistry

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By — McGraw-Hill Professional
Updated on Feb 1, 2011

Review the following concepts if necessary:

Problems

Answer the following questions. You have 20 minutes. You may not use a calculator. You may use the periodic table.

Choose the type of energy that best relates to questions 1–4.

    1. free energy
    2. lattice energy
    3. kinetic energy
    4. activation energy
    5. ionization energy
  1. the minimum energy required to initiate a reaction
  2. the minimum energy required for a nonspontaneous reaction
  3. The average ____________ is the same for any ideal gas at a given temperature.
  4. the energy released when the gaseous ions combine to form an ionic solid
  5. Given the following information:
  6. C(s) + O2(g) → CO2(g) ΔH = –393.5 kJ

    H2(g) + (l/2) O2(g) → H2O(l)

      ΔH = –285.8 kJ

    C2H2(g) + (5/2) O2(g) → 2 CO2(g) + H2O(l)

      ΔH = –1299.8 kJ

    find the enthalpy change for:

    2C(s) + H2(g) → C2H2(g)

    1. 454.0 kJ
    2. –227.0 kJ
    3. 0.0 kJ
    4. 227.0 kJ
    5. –454.0 kJ
  7. A sample of gallium metal is sealed inside a well-insulated, rigid container. The temperature inside the container is at the melting point of gallium metal. What can be said about the energy and the entropy of the system? Assume the insulation prevents any energy change with the surroundings.
    1. The total energy increases. The total entropy will increase.
    2. The total energy is constant. The total entropy is constant.
    3. The total energy is constant. The total entropy will decrease.
    4. The total energy is constant. The total entropy will increase.
    5. The total energy decreases. The total entropy will decrease.
  8. When ammonium chloride dissolves in water, the temperature drops. Which of the following conclusions may be related to this?
    1. The hydration energies of the ions are very high.
    2. Ammonium chloride produces an ideal solution in water.
    3. The heat of solution for ammonium chloride is exothermic.
    4. Ammonium chloride has a low lattice energy.
    5. Ammonium chloride is more soluble in hot water.
  9. Choose the reaction expected to have the greatest increase in entropy.
    1. H2O(g) → H2O(1)
    2. C(s) + O2(g) → CO2(g)
    3. Ca(s) + H2(g) → CaH2(s)
    4. N2(g) + 3H2(g) → 2 NH3(g)
    5. 2 KClO3(s) → 2 KCl(s) + 3 O2(g)
  10. Under standard conditions calcium metal reacts readily with chlorine gas. What conclusions may be drawn from this fact?
    1. Keq < 1 and ΔG° > 0
    2. Keq > 1 and ΔG° = 0
    3. Keq < 1 and ΔG° < 0
    4. Keq > 1 and ΔG° < 0
    5. Keq > 1 and ΔG° > 0
  11. Which of the following combinations is true when sodium chloride melts?
    1. ΔH > 0 and ΔS > 0
    2. ΔH = 0 and ΔS > 0
    3. ΔH > 0 and ΔS < 0
    4. ΔH < 0 and ΔS < 0
    5. ΔH < 0 and ΔS > 0
  12. Which of the following reactions have a negative entropy change?
    1. 2 H2(g) + O2(g) → 2 H2O(l)
    2. 2 NH3(g) → N2(g) + 3 H2(g)
    3. Ca(s) + Cl2(g) → CaCl2(s)
    1. II only
    2. I only
    3. I, II, and III
    4. III only
    5. I and III
  13. A certain reaction is non-spontaneous under standard conditions, but becomes spontaneous at higher temperatures. What conclusions may be drawn under standard conditions?
    1. ΔH < 0, ΔS > 0, and ΔG > 0
    2. ΔH > 0, ΔS < 0, and ΔG > 0
    3. ΔH > 0, ΔS > 0, and ΔG > 0
    4. ΔH < 0, ΔS < 0, and ΔG > 0
    5. ΔH > 0, ΔS > 0, and ΔG = 0
  14. 2 H2(g) + O2(g) → 2 H2O(g)
  15. From the table below, determine the enthalpy change for the above reaction.

    1. 0 kJ
    2. 485 kJ
    3. –485 kJ
    4. 464 kJ
    5. 443 kJ
  16. What is the energy required to convert a gaseous atom, in the ground state, to a gaseous cation?
    1. ionization energy
    2. kinetic energy
    3. activation energy
    4. lattice energy
    5. free energy
  17. Which of the following reactions would be accompanied by the greatest decrease in entropy?
    1. N2(g) + 3 H2(g) → 2 NH3(g)
    2. C(s) + O2(g) → CO2(g)
    3. 2 H2(g) + O2(g) → 2 H2O(g)
    4. 2 Na(s) + Cl2(g) → 2 NaCl(s)
    5. 2 KClO3(s) → 2 KCl(s) + 3 O2(g)
  18. CO(g) + 2 H2(g) → CH3OH(g) ΔH = –91kJ
  19. Determine ΔH for the above reaction if CH3OH(l) were formed in the above reaction instead of CH3OH(g). The ΔH of vaporization for CH3OH is 37 kJ/mol.

    1. –128 kJ
    2. –54 kJ
    3. +128 kJ
    4. +54 kJ
    5. –37 kJ
  20. A solution is prepared by dissolving solid ammonium nitrate, NH4NO3, in water. The initial temperature of the water was 25°C, but after the solid had dissolved, the temperature had fallen to 20°C. What conclusions may be made about ΔH and ΔS?
    1. ΔH < 0     ΔS > 0
    2. ΔH > 0     ΔS > 0
    3. ΔH > 0     ΔS < 0
    4. ΔH < 0     ΔS < 0
    5. ΔH = 0     ΔS > 0
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