The Ka of the acid is 1.3 * 10^ -7.
Ka is the constant of dissociation of the acid.
Kb is the constant of dissociation of the conjugated base
The relationship between Ka and Kb is:
Ka * Kb = Kw = 1 * 10 ^-`14
=> Kb = Kw / Ka
=> Kb = [1 * 10 ^ -14 ] / [1.3 * 10 ^ -7] = 7.69 * 10 ^-8 = 7.7 * 10 ^ -8
Answer: 7.7 * 10^-8
