An acid is a source of aqueous H+(aq). For example, HCl(aq) is the acid in your stomach:
HCl(aq) ! H+(aq) + Cl{(aq). In a healthy stomach, pH is regulated naturally and digestion
functions properly when the pH is around 3 (recall neutral is pH = 7). Excess stomach acid can
be combated with bases, or antacids". Bases are H+(aq) acceptors; in water, they provide species
that can react with H+(aq).
Common ingredients in antacids are metal hydroxide and metal carbonate salts. The hydroxides
provide hydroxide ion, OH{, which can react with H+(aq) to form H2O. Carbonates provide the
carbonate ion, CO3
2{, which can react with H+(aq) to form H2O and CO2. The reactions of interest
in this lab are neutralization reactions.