A 100.0-mL sample of 0.503 M H₂A (diprotic acid)is titrated with 0.200 M NaOH.After 125.0 mL of 0.200 M NaOH has been added,the pH of the solution is 4.50.Calculate K_a1 for H₂A.

Question

Quizplus · Accepted Answer

At the first equivalence point of a diprotic acid titration, the pH is determined by the second dissociation constant, Ka2. However, since the pH is given as 4.50, it suggests that the solution is at the first equivalence point, and the pH is related to the average of pKa1 and pKa2. Given the pH and the stoichiometry, Ka1 can be calculated using the Henderson-Hasselbalch equation and the known concentrations.

A 1000-ML Sample of 0 ×\times× 10-10 B)4 ×\times× 10-5 D)not Enough Information to Calculate E)none of These

A 1000-ML Sample of 0 $\times$ 10^-¹⁰
B)4 $\times$ 10^-⁵
D)not Enough Information to Calculate
E)none of These