Consider the titration of 200.0 mL of a 0.100 M solution of the weak acid H₂A with 0.200 M NaOH. The first equivalence point is reached after 100.0 mL of 0.200 M NaOH has been added, and the pH is 6.27. The pH after 65.0 mL of 0.200 M NaOH has been added, the pH is 4.95.Calculate the value of K_a1 for H₂A. A) 2.10 × 10^-5 B) 5.37 × 10^-7 C) 1.40 × 10^-8 D) 1.12 × 10^-5 E) none of these

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Quizplus · Accepted Answer

At the half-equivalence point, pH = pKa1. After 65 mL of NaOH, the solution is at the half-equivalence point, so pKa1 = 4.95. Therefore, Ka1 = 10^-4.95 = 2.10 × 10^-5.

Consider the Titration of 200