- Aligned with Big Idea 3 and Learning Objective 3.3
- Emphasizes Science Practices 2, 3, 4, 5, and 7
Determine the molar ratio of reactants in 2 acid-base reactions using the method of continuous variation. Teach this activity using either the guided activity or inquiry activity. In the guided activity, students react volumes of acid and base in different ratios and graph the temperature changes. The volume ratio that produces the largest temperature change is the correct stoichiometry of the reaction. From their data, students identify their unknown acid from a list of 9 possibilities.
In the inquiry activity, students design an experiment to determine the stoichiometry of an acid-base reaction. The inquiry activity provides an opportunity for students to present their experiment’s design and results, reinforcing the practice of communicating findings. Detailed preparation and procedure notes guide you through leading a successful inquiry exercise, including a suggested rubric for assessing student performance.
Both activities include Big Idea assessment questions that follow the format of the AP® Chemistry Exam free-response questions. In the Big Idea assessment, students apply their new knowledge of continuous variation to determine the stoichiometry of a reaction between lead ion and iodide ion. Students determine the formula of the product and the oxidation number of the lead ion. In the second question, students use data provided to determine the stoichiometry of a reaction between iron ion and a ligand to form a complex.
This kit provides the following AP® Chemistry experiences: design a procedure to collect data, analyze data, plot data, calculate molar ratios, write and balance chemical equations, and note indicators that a chemical change has occurred. Materials are sufficient for 30 students working in teams of 3. Digital teacher’s manual, included FREE with kit purchase or sold separately, is a 12-month eBook license to the Stoichiometry of Chemical Reactions teacher’s manual. You can also access the digital student guide for this kit for free at
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