Identification of Unknown Chloride Salts Using a Combination of Qualitative Analysis and Titration with Silver Nitrate: A General Chemistry Laboratory

General chemistry students often have difficulty writing balanced equations and performing stoichiometry calculations for precipitation reactions, in part because of difficulty understanding the symbolic notation used to represent chemical reactions. We have developed a problem-based experiment to improve student learning of these concepts, and student surveys indicate this goal was achieved. Furthermore, this experiment requires students to integrate results from several different experiments and emphasizes critical-thinking and problem-solving skills. Students identify unknown chloride salts by (1) using a precipitation reaction to determine if the cation is a group 1 or group 2 metal, (2) performing a titration with silver nitrate to determine the formula mass of the salt, and (3) confirming the identity of the salt using a flame test. Students enjoyed the lab, and over 75% of the unknowns were correctly identified.