Abstract
Closed-form algebraic expressions for the pH of ideal weak acid and weak
acid buffer solutions (and their titration with a strong base) were
obtained and analyzed with the aid of computer algebra systems. These
expressions are used to evaluate, without the use of numerical
approximations, the precision and accuracy of different approximations
commonly employed to calculate the pH. The closed-form expression for
the pH of a buffer solution is used to obtain an analytical expression
for the pH stability when a strong base is added. Finally, it is shown
that the pH expressions for all the systems under study can be obtained
from an unique closed-form expression in terms of an effective weak acid
constant and an effective acid concentration.