Formic acid is a buffer containing .50M H2C6H6O6 and .75M NaHC6H6O6. what is the pH if Ka= 6.8 x 10^ -5

Question

(PLEASE SHOW ALL WORK FOR THIS EQUATION)

A. 3.36

B. 3.59

C. 3.95

D. 4.18

Answer 1

H2C6H6O6  looks more like ascorbic acid,

H2C6H6O6 --> H+  &   HC6H6O6-

K = [H+]  [HC6H6O6-] / H2C6H6O6]

6.8e-5 =  [H+]  [0.75] / [0.50]

[H+] = 4.53e-5

pH = 4.34

that's the answer i get, check the data

K ascorbic is closer to 8.0e-5

K formic is closer to 1.8e-4