A diprotic acid H₂A is titrated with 0.100 M NaOH. Two distinct equivalence points are observed at 25.0 mL and 50.0 mL of base added. The pH values at 12.5 mL and 37.5 mL of base are 2.90 and 7.25, respectively.
Which pair of Ka values is most consistent with these data?
a) Ka1=8.0×10−3 and Ka2=5.6×10−7
b) Ka1=1.3×10−3 and Ka2=5.6×10−8
c) Ka1=5.6×10−8 and Ka2=1.3×10−3
d) Ka1=8.0×10−12 and Ka2=1.8×10−7