The following partial data were collected while titrating 25.0 mL of a monoprotic weak acid of unknown concentration with 0.100 M KOH at 25 °C.
Volume KOH added (mL): 0.00 | 12.50 | 25.00
Measured pH: 3.10 | 4.78 | 8.65
What is the approximate pKa of the acid?
a) 8.65
b) 5.08
c) 4.78
d) 3.10