Degree of Ionization for a Weak Acid or Base

NOTE: The following applies to a weak monoprotic acid or base (dissociation constant < 1).

percent ionization =

= (molar concentration of conjugate acid or base) * 100 / (analytical concentration of the acid or base)

where:

• The molar concentration of the conjugate acid is the [H3O+].

• The molar concentration of the conjugate base is the [OH-].

• K is the dissociation constant (Ka for acid, Kb for base).

[H3O+] for a weak acid or [OH-] for a weak base =

= 0.5 * (X – K)

X =

= SQRT((K^2) + (4 * K * (molarity of the acid or base in solution)))