A simple undergraduate experiment for the quantitative analysis of acetic acid in household vinegar and ascorbic acid in vitamin-C supplement tablets is presented. The laboratory experiment combines titration concept with electrolysis and an application of the gas laws. The vinegar sample was placed in the cathode compartment of the electrolysis cell. Electrolysis of water generated OH-(aq) in the cathode compartment. Acetic acid in the vinegar sample was neutralized by electrolytically generated OH-(aq). Phenolphthalein was used as a visual indicator to detect the end point of the titration. The volume of O2(g) produced at the anode was monitored. The amount of OH-(aq) produced at the cathode was determined from the volume of O2(g) produced at the anode. The amount of acetic acid present in the sample was determined from the mole relationships between H+(aq), OH-(aq), and O2(g). The concentration of acetic acid in household vinegar was determined to be 4.8%. The method was also used for the analysis of vitamin-C tablets. The electrolysis cell was directly powered by a 9-V battery. Preparation of an electrolysis cell, experimental procedure, and the results of the electrolytic titration will be presented.

Using mole ratios of electrolytic products of water: A modified coulometric analysis experiment in the undergraduate laboratory

243rd National Meeting (2012)

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