The pH of a buffer solution made from a weak acid and its salt depends on
Correct answer: D. the dissociation constant of the acid and the ratio of salt to acid concentration
- A. the total volume of the solution
- B. the temperature only
- C. the presence of a catalyst
- D. the dissociation constant of the acid and the ratio of salt to acid concentration
Explanation
The Henderson Hasselbalch relationship gives pH as pKa plus the logarithm of the ratio of salt to acid, so it is the ratio that matters rather than the absolute amounts. Diluting the buffer changes both concentrations equally and so leaves the pH almost unaltered, which is one of its most useful features. Buffer capacity, however, does depend on how concentrated the components are.
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About Buffer Solutions
Buffer solutions resist changes in pH when small amounts of acid or base are added, using a weak acid and its conjugate base or a weak base and its conjugate acid. Work includes buffer action, the common-ion effect, Henderson-Hasselbalch calculations, buffer capacity, and the difference between acidic and basic buffers.
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