Alka Seltzer Strength

Learning Objectives:

Students determine the percentage of sodium bicarbonate in a commercial Alka Seltzer tablet.


Students dissolve Alka Seltzer tablets in different solutions of water-vinegar. By adding vinegar to the solution, more sodium bicarbonate reacts; adding an excess of vinegar results in complete reaction of the NaHCO₃, causing Alka Seltzer to become the limiting reactant. By plotting a graph of the calculated percent mass of NaHCO₃ in the tablet vs. the amount of vinegar in the water-vinegar solution, students find the amount of NaHCO₃ in the Alka Seltzer tablet.