Weak acids, unlike strong acids, do not fully dissociate in aqueous solution but instead reach a dynamic equilibrium between the undissociated acid and its ionization products, governed by an acid dissociation (equilibrium) constant, Ka. The relative strength of hydrohalic acids depends on bond strength between hydrogen and the halogen, which correlates with electronegativity and atomic size; fluorine's high electronegativity and small size create an unusually strong H–F bond, making hydrofluoric acid weak despite fluorine's high electronegativity generally favoring acidity. Solving for equilibrium concentrations in a weak acid system requires setting up an equilibrium expression from initial concentration and an unknown dissociated amount (x), yielding a quadratic equation whose exact or approximated solution gives the hydrogen ion concentration and, via the negative logarithm, the solution's pH.
Weak acids, unlike strong acids, do not fully dissociate in aqueous solution but instead reach a dynamic equilibrium between the undissociated acid and its ionization products, governed by an acid di…