The pH of a solution is 5, the hydroxyl ion concentration in mol dm3 is

Correct answer: B. 109

  • A. 10-5
  • B. 109
  • C. 105.5
  • D. 10-7

Explanation

To find the hydroxyl ion concentration, we first determine the pOH from the given pH. The relationship is pH + pOH = 14. With a pH of 5, the pOH is 14 - 5 = 9. The hydroxyl ion concentration is then calculated as 10 to the power of negative pOH, which is 10-9 mol dm3. Option A represents the hydrogen ion concentration, not hydroxyl ion concentration. Option C does not fit the calculation. Option D represents a neutral condition and is not relevant to this acidic solution.

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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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