MCAT General Chemistry Question 149: Answer and Explanation
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Question: 149
14. What is the approximate pH of a 1.2 × 10?5 M aqueous solution of NaOH?
- A. 4.92
- B. 7.50
- C. 9.08
- D. 12.45
Correct Answer: C
Explanation:
NaOH is a strong base; as such, there will be 1.2 × 10-5 M OH- in solution. Based on this information alone, the pOH must be between 4 and 5, and the pH must be between 9 and 10. Using the shortcut, pOH ≈ 5 - 0.12 = 4.88. pH = 14 - pOH = 9.12 (actual = 9.08).