Question

A 0.303 g sample of Tums (containing CO2−3CO32- ) is dissolved in 25.0 mL of 0.102 M HCl. The hydrochloric acid that is not neutralized by the Tums is back titrated with 8.04 mL of 0.102 M NaOH. How many mol of base are in the antacid?

Answer 1

moles of HCl = 25 x 0.102 / 1000 = 2.55 x 10^-3

moles of NaOH = 8.04 x 0.102 / 1000 = 8.20 x 10^-4

moles of HCl reacted with antacid = 2.55 x 10^-3 - 8.20 x 10^-4

                                                      = 1.73 x 10^-3

moles of HCl = moles of antacid

so

moles of antacid = 1.73 x 10^-3