In the titration of a weak acid with a strong base, the equivalence point is Blank 1 Question 8[select: , above, below] 7. This is due to the formation of Blank 2 Question 8[select: , a conjugate acid of a weak base, a conjugate base of a weak acid] .

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The equivalence point in the titration of a weak acid with a strong base is above 7 because the weak acid is converted to its conjugate base, which hydrolyzes to produce OH−. 1) Relevant knowledge points and concepts - Equivalence point: point where stoichiometric amounts of acid and base have reacted. - Weak acid (HA) neutralized by strong base (OH−) yields its conjugate base (A−) in solution. - Conjugate base hydrolysis: A− + H2O ⇌ HA + OH−, which produces hydroxide ions and makes the solution basic. - Relationship between Ka and Kb: Kb = Kw / Ka (Kw = 1.0×10−14 at 25 °C). 2) Step-by-step reasoning - At equivalence, all HA has been converted to A−; no free HA remains (ignoring buffer region). - The solution contains the salt A− (from the weak acid) and the conjugate cation (from the strong base, e.g., Na+), which is spectator. - A− acts as a base and reacts with water to generate OH−, raising pH above 7. - Quantitatively, for initial conjugate base concentration C, the hydrolysis equilibrium: Kb = [HA][OH−] / [A−]. Assuming x = [OH−] produced and x << C, x ≈ sqrt(Kb · C). 3) Example calculation (intermediate steps) - Suppose Ka = 1.0×10−5 → Kb = 1.0×10−9. - If C = 0.10 M, then [OH−] ≈ sqrt(1.0×10−9 × 0.10) = sqrt(1.0×10−10) = 1.0×10−5 M. - pOH = 5.00 → pH = 14.00 − 5.00 = 9.00 (clearly > 7). 4) Why the correct answer is correct - Because A− produces OH− by hydrolysis, the equivalence point is basic (pH > 7). The species formed is specifically the conjugate base of the weak acid. 5) Why the other options are incorrect - “Below 7” would imply acidity at equivalence; that occurs when titrating a weak base with a strong acid, not a weak acid with a strong base. - “A conjugate acid of a weak base” is not formed here; the titration produces A− (conjugate base of HA), not a conjugate acid. 6) Conclusion - Therefore, the equivalence point is above 7 due to the formation of a conjugate base of a weak acid, which matches the provided answer: "above" and "a conjugate base of a weak acid."

In the titration of a weak acid with a strong base, the equivalence point is Blank 1 Question 8[select: , above, below] 7. This is due to the formation of Blank 2 Question 8[select: , a conjugate acid of a weak base, a conjugate base of a weak acid] .多重下拉选择题

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