The pH of a solution is 5. The hydroxyl ion concentration in mol·dm⁻³ is:
Correct answer: B. 10⁻⁹
- A. 10⁻⁵
- B. 10⁻⁹
- C. 10⁵⋅⁵
- D. 10⁻⁷
Explanation
The relationship between pH and pOH is pH + pOH = 14. If the pH is 5, the pOH is 14 - 5 = 9. The hydroxyl ion concentration is [OH⁻] = 10⁻pOH = 10⁻⁹ M.
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About Acids, Bases and Salts
Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.
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