Answer:
pH = 11.9
Explanation:
The solution is 0.93M. The pKb is 4.19
The general equation of a weak base, X, is:
Kb = [OH⁻] [XH⁺] / [X]
Where Kb is 10^-pKb = 6.457x10⁻⁵
[OH⁻] and [XH⁺] comes both from the same equilibrium and its concentration, X, is the same = [OH⁻] = [XH⁺] = X
And [X] could be taken as the initial concentration of the weak acid, 0.93M
Kb = [OH⁻] [XH⁺] / [X]
6.457x10⁻⁵ = X² / 0.93M
6x10⁻⁵ = X²
X = 7.749x10⁻³M = [OH⁻]
As pOH = -log[OH⁻]
pOH = 2.11
pH = 14 - pOH
pH = 11.9
