<P> The calculation of the pH of a solution containing acids and / or bases is an example of a chemical speciation calculation, that is, a mathematical procedure for calculating the concentrations of all chemical species that are present in the solution . The complexity of the procedure depends on the nature of the solution . For strong acids and bases no calculations are necessary except in extreme situations . The pH of a solution containing a weak acid requires the solution of a quadratic equation . The pH of a solution containing a weak base may require the solution of a cubic equation . The general case requires the solution of a set of non-linear simultaneous equations . </P> <P> A complicating factor is that water itself is a weak acid and a weak base (see amphoterism). It dissociates according to the equilibrium </P> <Dl> <Dd> 2 H 2 O ↽ − − ⇀ H 3 O + (aq) + OH − (aq) (\ displaystyle (\ ce (2H2O <=> (H3O+ (aq)) + (OH ^ (-) (aq))))) </Dd> </Dl> <Dd> 2 H 2 O ↽ − − ⇀ H 3 O + (aq) + OH − (aq) (\ displaystyle (\ ce (2H2O <=> (H3O+ (aq)) + (OH ^ (-) (aq))))) </Dd>

How much more acidic is a solution with ph 3 than one of ph 6