The latter are produced when the acid molecules lose H + ions to water.. HA(aq) + H 2 O(l) H 3 O + (aq) + A-(aq) This page explains the terms strong and weak as applied to acids. When an uncharged weak acid is added to water, a homogeneous equilibrium forms in which aqueous acid molecules, HA(aq), react with liquid water to form aqueous hydronium ions and aqueous anions, A-(aq). It can be written that Ka [H+][A- ]/[HA]. It is important that you don't confuse the words strong and weak with the terms concentrated and dilute.. As you will see below, the strength of an acid is related to the proportion of it which has reacted with water to produce ions. K a is commonly expressed in units of mol/L.

The ionization of an acid in water measures the relative strength of the acid. The Ka is simply the equilibrium constant for the ionization of an acid HA into H+ and A- . Considering the degree of dissociation to be α we can easily establish the formula involving α , C (=concentration of the solution) and Ka , which is written above. The generic equilibrium constant expression for a weak acid is written as follows.
As a part of this it defines and explains what is meant by pH, K a and pK a.. The acid dissociation constant is the equilibrium constant of the dissociation reaction of an acid and is denoted by K a.This equilibrium constant is a quantitative measure of the strength of an acid in a solution. If the acid is strong enough to ignore the dissociation of water, the H 3 O + ion and A-ion concentrations in this solution are about equal.