A New Teaching Laboratory Experiment to Address the Effect of pH on Solubility

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 22 (2017) pp 70-72

A New Teaching Laboratory Experiment to Address the Effect of pH on Solubility

Juan Schmidt^† and Raúl Esteban Ithuralde*^,‡

^†Undergraduate Student of Chemistry at Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires; ^‡Instituto de Estudios para el Desarrollo Social; Facultad de Humanidades, Ciencias Sociales y de la Salud; Universidad Nacional de Santiago del Estero y Departamento de Química Inorgánica, Analítica y Química Física; Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, ithu@qi.fcen.uba.ar
Received September 15, 2016. Accepted January 20, 2017.

Published: 27 March 2017

Abstract. This paper presents a teaching experience involving an experiment based on the potentiostatic and electrochemical titration of a silver acetate solution with sodium hydroxide, a chemical system where at least three chemical equilibria are involved. It is known that natural samples are inherently complex, and several different chemical equilibria are simultaneously present. That is why we believe the understanding of complex systems is essential for carrying out chemical analysis. Solubility of many compounds is highly dependent on pH and many of the exercises in the inorganic chemistry classroom are focused on calculating the solubility of different species at different pHs, most of the times using speciation coefficients. However, the dependence of solubility on pH is usually analyzed in a point by point basis. This experiment, which only requires equipment usually available in any general chemistry teaching laboratory, allows students to analyze both a complex system and the dynamic nature of solubility when pH changes continuously in time. It gives them the possibility to reach a broader understanding of simultaneous chemical equilibria. Thus, we consider it to be an excellent complement to typical chemistry exercises.

Key Words: Laboratories and Demonstrations; general chemistry; chemical equilibria; combined chemical equilibria

(*) Corresponding author. (E-mail: ithu@qi.fcen.uba.ar )

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Supporting Materials:

One PDF file for the laboratory proceedure is available. (74 KB)