Grades 9–12. Students react vinegar and Alka-Seltzer® in varying ratios and graph their data to determine the stoichiometry of this acid-base reaction. From the graph, students can also determine the amount of sodium bicarbonate in Alka-Seltzer® tablets and calculate the percent error between their value and the value printed on the product label. The use of everyday chemicals makes this experiment fun, safe, and easier to clean up than traditional stoichiometry experiments.