Determining the Acetic Acid Concentration in White Vinegar: An At-Home Undergraduate Chemistry Experiment During the COVID-19 Pandemic

Abstract

Due to the COVID-19 pandemic, many university-level chemistry laboratory experiments transitioned online. This created an educational challenge because students are unable to access reagents and instruments typical in a university lab setting. It is also difficult for students to connect theory to practice since real-lab experimentation is not possible in a virtual online for-mat. In our online Introductory Quantitative Analysis Laboratory course (GW Chem 2123W) in spring 2021, students were required to design and perform an experiment that could be safely conducted at home which can also demonstrate key princi-ples of quantitative analysis. Herein, we conducted a reliable at-home experiment that utilizes university-level acid/base titra-tion techniques to determine the acetic acid concentration in white vinegar. The experiment used sodium bicarbonate in the form of baking soda to titrate the Whole Foods white vinegar which is advertised to contain 6% of acetic acid. We reliably obtained an equivalence point for the titration from which the actual concentration of acetic acid in the vinegar was calculated with error analysis to be 19% higher than the advertised value. The analytical techniques demonstrated in this experiment supplement practical knowledge of acid/base techniques learned in the online classroom and prompt adoption of this meth-odology in online laboratory curriculum. This experiment can also be readily applied to measure other acidic solutions such as vinegar and juice for at-home experiment

A Simple At-Home Titration: Quantifying Citric Acid in Lemon Juice with Baking Soda and Mentos

“…At-home pH meters can also be used to track reaction progress and determine the titration end point. 13,20,22 However, pH meters are a specialty item that must be purchased or rented by the student at extra expense.…”

“…Multiple approaches to at-home titrations have recently been reported in the literature. The quantity of titrant added can be tracked with a kitchen scale or a syringe. − The end point of the titration can be tracked with a pH sensitive natural dye, such as turmeric , or red cabbage . However, these natural dyes sometimes give only subtle color differences with a change in pH and therefore required students to employ RGB image analysis to aid in the determination of the end point of a titration.…”

“…To further ensure this reaction runs to near completion, Parel et al gently heated their solutions to 37 °C with the stated purpose of reducing carbon dioxide concentration at equilibrium. 20 However, heating the solution may also provide additional challenges (through the need of additional equipment) and safety issues (potential for burns, etc.) for an athome titration, which should be avoided if possible.…”

“…However, these natural dyes sometimes give only subtle color differences with a change in pH and therefore required students to employ RGB image analysis to aid in the determination of the end point of a titration. At-home pH meters can also be used to track reaction progress and determine the titration end point. ,, However, pH meters are a specialty item that must be purchased or rented by the student at extra expense.…”

“…An additional drawback of the above approaches is that they were sometimes not assessed for accuracy, instead focusing on student perceptions. , In some cases, the analyte concentration values were compared to manufacturers’ values, which generally showed reasonable results with average percent errors of 5–20%. − Comparisons with manufacturers’ values provides a helpful comparison, but an ideal benchmark for an at-home experiment performed by undergraduates is comparison to typical results of a similar experiment performed in-person. Here, at-home titration (eq ) results are directly compared to the traditional in-person titration (eq ) (sodium hydroxide/phenolphthalein) performed by the same students.…”