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AN AT-HOME TITRATION USING BAKING SODA, LEMON JUICE, AND MENTOS©.

Abstract

The ongoing trend towards increased online and hybrid instruction accelerated during the pandemic. To effectively provide laboratory experiences to students in these modalities it is essential that suitable at-home experiments are developed. In this work, we demonstrate an experiment which can quantify the concentration of citric acid in lemon juice via titration with baking soda without the use of any specialized equipment. Although sodium bicarbonate is a weak base, the gas evolution of carbon dioxide drives the reaction to near completion via Le Chatelier’s Principle. Further, we add the candy Mentos to the analyte during titration which provides a nucleation site for carbon dioxide and ensures the gas evolution is rapid. The cessation of this vigorous gas evolution also provides an easy way to monitor the completion of this acid-base reaction. During the summer of 2021, a group of general chemistry students at Georgia Gwinnett College performed this experiment at-home and compared their results with the traditional in-person titration (performed with sodium hydroxide). The concentration of citric acid determined by the at-home procedure was of 0.20 M (±0.08 M) which was within one standard deviation of the results of the in-person titration (0.25 M (±0.03 M)).

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