Question detail
In a titration curve, what does the buffer region indicate?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Acids and bases (A-level only)
Question
- A. A region where the pH changes rapidly
- B. A region where the solution resists changes in pH
- C. A region where no acid or base is present
- D. A region where the equivalence point occurs
Answer
A region where the solution resists changes in pH
Explanation
The buffer region in a titration curve indicates where the solution can resist changes in pH upon the addition of small amounts of acid or base, due to the presence of a weak acid and its conjugate base.
Common mistake
Misunderstanding pH Curve Shapes
Students often incorrectly assume that the pH curve for a weak acid-strong base titration will have a steep slope throughout the entire range, similar to that of a strong acid-strong base titration.
To correct this, remember that the pH curve for a weak acid-strong base titration will show a more gradual slope before the equivalence point due to the weak acid's partial dissociation. The formula for pH at the equivalence point can be derived from the concentration of the conjugate base formed. For example, if you have a weak acid HA with a concentration of 0.1 mol/dm³ and a Ka of 1.8 x 10^-5, you can calculate the pH at the equivalence point using the formula: pH = 14 - 0.5 * pKa, where pKa = -log(Ka). Substituting gives pH = 14 - 0.5 * 4.74 = 11.63. Therefore, the pH at the equivalence point is 11.63.
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