Acid–base titration concepts and experiments are ubiquitous, yet challenging, aspects of the general chemistry curriculum. Most general chemistry courses include at least one acid–base titration laboratory experiment, though the focus is often on determining the concentration, pK a, or molar mass of an analyte rather than on the details of interpreting a titration curve more broadly. This article describes the transformation of a single-period, traditional confirmation laboratory experiment into a multiweek, guided-inquiry capstone experience investigating a phosphate buffer system. The revision was designed to improve student understanding of the composition of a buffer system, the chemical reactions occurring as the buffer is titrated with a strong acid, and the rationale behind a method for determining the concentration of the buffer components. An experimental design component was incorporated in which groups of students formulated their own procedure to determine the concentration of the buffer components in an unknown sample. Preliminary evidence regarding the success of the implementation of this guided-inquiry experience was obtained through student work submitted for the titration and experimental design activities, student comments from the course evaluation and a self-reflection exercise, and midterm and final exam assessment questions.
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