Question

The ph of a 0.013m weak monoprotic acid solution is 5.27. calculate ka for this acid

Answer 1

Given:

pH is 5.27
Concentration of sol'n 0.013m (weak monoprotic)

Determine H+ concentration:

[H+] = 10^-pH
        = 10^-5.27
        = 5.37x10^-6 

Ka = [H+] [A-] / [HA]
      = (5.37x10^-6) * (5.37x10^-6) / (0.013 - 5.37x10^-6)
      = 2.22x10^-9