Question

Determine the pH of a 0.18 M H2CO3 solution. Carbonic acid is a diprotic acid whose Ka1 = 4.3 ×
10-7 and Ka2 = 5.6 × 10-11.
10)
A) 10.44 B) 5.50 C) 4.31 D) 11.00 E) 3.56

Answer 1

pH comes essentially from only the Ka1

Ka1 = [H+] [HCO3] / [H2CO3]

4.3 x 10^-7 = [x] [x] / [0.18]

x2 = 7.74 e-8

x = [H+] = 2.78 e-4

pH = 3.56

your answer is

E) 3.56