A 25.0 mL sample of a monoprotic weak acid is titrated with 0.100 M NaOH. The equivalence point occurs after 30.0 mL of base has been added. The pH measured after exactly 15.0 mL of base is 4.75.
What is the value of Ka for the acid?
a) 5.6×10−5
b) 1.1×10−5
c) 1.8×10−5
d) 5.6×10−10