Consider the Titration of 200

Multiple Choice

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