MCAT General Chemistry Freestanding Practice Questions: Thermodynamics

1. Which one of the salts in Table 1 has the smallest value of ∆G^o_diss?

• A. absorbed during the breaking of H—H bonds and the reaction is spontaneous.
• B. released during the formation of H—H bonds and the reaction is nonspontaneous.
• C. absorbed during the formation of O=O bonds and the reaction is spontaneous.
• D. released during the breaking of O—H bonds and the reaction is nonspontaneous.

2. Lyophilization would most likely be employed industrially in which of the following separations?

• A. Decreasing volume
• B. Increasing temperature
• C. Decreasing temperature
• D. The reaction will always be nonspontaneous.

3. The summit of Mount Everest is 8.8 km above sea level. What is the approximate density of air at this point?

• A. N₂
• B. Br₂
• C. Hg
• D. Al

4. If Step 1 were simply a fast reaction and not a fast equilibrium, what would be the expected rate law for the decomposition of nitramide in water?

• A. ∆H_fus = -20 kJ/mol, DH_vap = 66.7 kJ/mol
• B. ∆H_fus = 40.7 kJ/mol, DH_vap = 6.0 kJ/mol
• C. ∆H_fus = 6.0 kJ/mol, DH_vap = 40.7 kJ/mol
• D. ∆H_fus = 12.0 kJ/mol, DH_vap = 81.4 kJ/mol

5. Which of the following best describes how a catalyst might speed up a reaction?

• A. CH₃COOH(l) → CH₃CHO(l) + ½ O₂(g)
• B. C₂H₅OH(l) + ½ O₂(g) → CH₃CHO(l) + H₂O(l)
• C. CH₃CHO(l) + ½ O₂(g) → CH₃COOH(l)
• D. C₂H₅OH(l) + O₂(g) → CH₃COOH(l) + H₂O(l)

6. The shape of the carbonate ion is:

• A. The rate constant for the unfavorable reactions is very large.
• B. The cycle contains exergonic reactions that drive the endergonic reactions forward.
• C. The endothermically unfavorable reactions also have a negative entropy change.
• D. The activation energies of the unfavorable reactions are lowered by catalysts.