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NDA 2025 GAT · General Knowledge · Acids, Bases and Salts · medium

The pH of a 0.001 M aqueous solution of sodium hydroxide (a strong base) at 25 degrees Celsius is

Single correct option

The pH of a 0.001 M aqueous solution of sodium hydroxide (a strong base) at 25 degrees Celsius is
  1. A. 11
  2. B. 3
  3. C. 10
  4. D. 12
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Answer: (A) 11

NaOH is a strong base and dissociates completely, so [OH-] = 10^-3 M and pOH = 3. Since pH + pOH = 14 at 25 degrees Celsius, pH = 11. The value 3 is the pH of a 0.001 M strong acid, so confusing the two is the usual trap.
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Original question written in the NDA 2025 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake