Gravimetric analysis is a classic technique for determining the mass of an analyte through precipitation. Because of the complex nature of gravimetric analysis, it can be a challenging experiment. In an article published in the Journal of Chemical Education, Jennifer Garcia and Linda Shultz compare a conductometric titration to conventional gravimetric analysis and conclude that the titration is less time consuming, more predictable, and less hazardous.1 The use of Vernier conductivity probes and Graphical Analysis 4 to perform and analyze a conductometric titration helps students develop skills and knowledge expected by the Next Generation Science Standards (NGSS) and state standards.
A titration is a quantitative analysis method used to determine the concentration of a substance in solution by adding a standard (titrant) and monitoring the result of the chemical reaction. Acid-base titrations are among the more common titration experiments. While less typical, conductometric titrations can augment experiments involving gravimetric analysis and make such experiments more accessible to students.
In “Determination of Sulfate by Conductometric Titration: An Undergraduate Laboratory Experiment,” Garcia and Schultz describe how students titrate a solution of K2SO4 with BaCl2, monitor the changes in conductivity, and manually graph the data. As the reaction proceeds, the resulting product BaSO4 precipitates out of solution, lowering the conductivity. The precipitation is complete at the equivalence point and by continuing to add BaCl2, the conductivity increases.
With a few small changes to the procedure developed by Garcia and Schultz, your students can complete a conductometric titration using Go Direct® Conductivity Probe. Data are automatically graphed in Graphical Analysis 4, and students can use the analysis tools to determine the equivalence point.
1 Garcia, J. & Schultz, L. “Determination of Sulfate by Conductometric Titration: An Undergraduate Laboratory Experiment.” Journal of Chemical Education, 2016, 93 (5), pp 910–14.