Question

write a balanced equation for the reaction of the active ingredient in Tums with excess acid.

Answer 1

There are two active components in Tums: magnesium carbonate and calcium carbonate. Normally, they are used to neutralize the main component of gastric acid - hydrochloric acid:
MgCO₃ + 2HCl = MgCl₂ + H₂O + CO₂;
CaCO₃ + 2HCl = CaCl₂ + H₂O + CO₂