In industrialized states every tenth adult suffers daily, and every third occasionally, from heartburn. In Germany almost ten million people are affected by this disease. Helpful medicines against heartburn are the so-called ‘antacids’.

Antacids bound acids against an over-acidification of the stomach. The stomach acid contains hydrochloric acid (HCl, dissolved in water), which reacts with the antacid to form water, carbon dioxide and the corresponding salt. Generally, antacids are carbonates. Very common is ‘Bullrichs salt’, which uses sodium hydrogen carbonate as active ingredient. A single dose of an antacid is to be chosen in a way that it will react with two grams of hydrochloric acid. You are to formulate the instruction leaflet for a pharmaceutical company, which sells calcium carbonate (CaCO3) as an antacid. The dosing instruction says that in case of heartburn, one tablet with sufficient water is to be ingested.

But the specification, how many grams of calcium carbonate one tablet contains, is still missing…