MCAT General Chemistry Question 230: Answer and Explanation

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Question: 230

8. If the K_sp of KI is 1.45 × 10^{- 6} in propanol at 25°C, what would the K_sp of KI be in propane at the same temperature?

A. 1.84
B. 2.90 × 10^-3
C. 1.81 × 10^-6
D. 7.56 × 10^-23

Correct Answer: D

Explanation:

D The golden rule of solubility is "like dissolves like." Potassium iodide is a salt held together by ionic forces and therefore comprised of charged ions. A salt will dissolve in a polar solvent better than a non-polar solvent. Propanol has a polar –OH group whereas propane is completely non-polar. Therefore, KI must have a smaller K_sp in propane than in propanol. The only answer that has a smaller K_sp value is choice D.

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