Based on the titration curves of a 1 M solution of a weak acid with a strong base and a 1 M solution of a strong acid with the same base, what is the estimated pKa of the weak acid?

• A. 4.7
• B. 3.5
• C. 7.0
• D. 9.2

Answer: (A)

Verified step by step guidance

1. Identify the equivalence point on the titration curve of the weak acid. This is where the amount of acid equals the amount of base added.
2. Determine the half-equivalence point on the titration curve. This is the point where half of the weak acid has been neutralized by the base.
3. At the half-equivalence point, the concentration of the weak acid equals the concentration of its conjugate base, and the pH at this point is equal to the pKa of the weak acid.
4. Examine the pH value at the half-equivalence point on the titration curve of the weak acid. This pH value is the estimated pKa of the weak acid.
5. Compare the pH value at the half-equivalence point with the given options (4.7, 3.5, 7.0, 9.2) to estimate the pKa of the weak acid.