H2CO3 -----------------------> H + HCO3-
1.61Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0Â Â Â Â Â Â Â Â Â Â Â
0 ---------------------> initial
1.61-x                                 Â
x           Â
x -------------------> equilibrium
Ka1 = [H+][HCO3-]/[H2CO3]
Ka1 = x^2 / 1.61-x
4.3 x 10^-7 = x^2 / 1.61-x
x^2 + 4.3 x 10^-7 x - 6.92 x 10^-7 = 0
x = 8.32 x 10^-4
[H+] = x = 8.32 x 10^-4 M
pH = -log [H+]
pH = -log (8.32 x 10^-4 )
pH = 3.08
