Introduction
We known an antacid is any substance, generally a base, which acts against stomach acidity. In other words, antacids are stomach acid neutralizers. The neutralizing capacity is the number of moles of acid needed to neutralize gram of the antacid. The base in antacids varies with the brand, for examples; aluminium hydroxide Al(OH)3, calcium carbonate CaCO3, magnesium carbonate MgCO3, magnesium hydroxide Mg(OH)2, and sodium bicarbonate NaHCO3.
For experiment, We known amount of HCl (the acid in stomach) is added to a measured amount of antacid. HCl will react with all of the antacid and still leave some extra HCl (excessed HCl). Then we will determine how much of the original HCl remains by titrating it to neutrality with a standardized solution of NaOH. Simple subtraction will show how much of the acid was neutralized by the antacid sample. This general method of analysis is called “back-titration”.