HC2HO3(aq)+H2O(l)⇄H3O+(aq)+C2HO3−(a q) pKa=3.18
at
25°C

The equilibrium for the acid ionization of HC2HO3 is represented by the equation above. If 10.0mL of 0.20MHC2HO3 react with 5.0mL of 0.10MNaOH, which of the following could be used to calculate the correct pH of the resulting solution?

A) pH=pKa+log(0.10/0.20)
B)pH=pKa+log(0.0050×0.10/0.0100×0.2 0)
C)pH=pKa+log[((0.0050×0.10/0.0150)/ ((0.0100×0.20)−(0.0050×0.10)0.0150) ]
D) pH=pKa+log[((0.0050×0.10)+(0.0100×0 .20)0.0150)/((0.0100×0.20)−(0.0050× 0.10)0.0150)]