Q12(a). Change in pH of an acetate buffer on adding HCl
A buffer solution contains 0.2 mole of acetic acid and 0.25 mole of potassium acetate per litre. Calculate the change in pH of the solution if 0.5 mL of 1 M HCl is added to it. The dissociation constant of acetic acid at room temperature is 1.75 × 10⁻⁵. (The volume change on the addition of HCl may be neglected).
Answer in brief
pH falls from 4.854 to 4.852: ΔpH = −0.002 (1 L of buffer); the same HCl in 1 L of pure water would lower the pH by 3.70.
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Coversbuffer solutionHenderson–Hasselbalch equationacetate bufferpH changebuffer capacity
All parts of Question 12
- 12(a) Change in pH of an acetate buffer on adding HCl10 marks
- 12(b) Activities of Na⁺ and SO₄²⁻ in a mixed electrolyte10 marks