MCAT General Chemistry Question 203: Answer and Explanation
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Question: 203
1. In the dissociation of phosphoric acid, the trend Ka1 > Ka2 > Ka3 is predominantly due to:
- A. II only
- B. III only
- C. II and III only
- D. I, II and III
Correct Answer: C
Explanation:
C Since water experiences hydrogen bonding, more energy is required to boil water compared with SH2, which leads to a higher boiling point, making Item I false and eliminating choice D. Since temperature is a measure of molecular motion, and hydrogen bonds bind molecules together, making this motion more difficult, hydrogen-bonded materials will require more energy to increase T and thus have high specific heats. Item II is true and choice B can be eliminated. The negative slope of the line between the solid and liquid phase on the phase diagram of water indicates that at higher pressures, liquid water is favored over solid, making Item III correct and C the best answer choice.