Practice question

MCQ

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A 0.05 M solution of a weak base B has a pH of 10. What is its Kb ?

Choose one · Correct answer highlighted

1.0 × 10⁻⁶ 2.0 × 10⁻⁷ Correct 5.0 × 10⁻⁸ 4.0 × 10⁻⁷

pH = 10 , pOH = 14 - 10 = 4 , [OH-] = 10⁻⁴ . For B + H₂O <=> BH+ + OH- , Kb = ([OH-]²/[B]) = ((10⁻⁴)²/0.05) = (10⁻⁸/0.05) = 2.0 × 10⁻⁷ .

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