Química analítica básica: neutralization volumetry - titration concepts and curves

Abstract

Volumetry is the generic term used to designate quantitative procedures that can be used in determining the concentration of species contained in a sample, known as analyte, by adding discrete and precise volumes of a solution of exactly known concentration. The reaction must be fast and quantitative. The so-called neutralization volumetry or acid-base volumetry is an analytical method based specifically on the reaction between the H₃O⁺ and OH^- ions: H₃O⁺ + OH^- = 2 H₂O whose extent is governed by the ionic product of water: K_H2O = [H3O⁺] [OH-] At first glance, one might think that the reaction between equivalent amounts of an acid and a base would always result in a neutral solution. However, this may not occur because of the hydrolysis and buffering phenomena that accompany the reactions between strong acids and weak bases or weak acids and strong bases. And, if the visual method for detecting the end point of the analytical procedure is chosen, the buffering effects generated in the reagent medium can still impair the action of the indicators and make it difficult to visualize the end point of the process. For these reasons, in order to correctly use neutralization volumetry, it is necessary to know very well the characteristics and behavior of the acid-base systems in aqueous solution involved in this analytical procedure, as well as their titration curves [1 -3].