Sodium Bicarbonate

Many commercial preparations of antacids contain sodium bicarbonate. Alka-Seltzer antacid contains sodium bicarbonate in addition to citric acid (C₆H₈O₇), which is used to dissolve the sodium bicarbonate. Pure baking soda will also relieve heartburn, but the citric acid in commercial antacids improves the taste and accelerates the disintegration of the tablet. When sodium bicarbonate is dissolved in water, the compound separates into ions, or charged particles, of sodium (Na⁺) and bicarbonate (HCO₃). The bicarbonate ions then react with acids as shown below. The symbol (aq), meaning aqueous, shows that the substance is dissolved in water; the symbol (g) refers to a gas, and (l) means a liquid. The hydrogen ions (H⁺) are from acids.

As shown above, one hydrogen ion and one bicarbonate ion react to produce a molecule of water and a molecule of carbon dioxide gas. This can be demonstrated at home by filling a reclosable plastic bag with one ounce (30 ml) of vinegar. The vinegar represents stomach acid. A teaspoon (5 ml) of baking soda (or an Alka-Seltzer tablet) is then dropped in the bag and the bag is quickly closed. The fizzing is caused by the production of carbon dioxide gas. The bag will quickly fill up with gas, demonstrating why many people burp after taking an antacid. This belching helps relieve the pressure that builds up in the stomach. In spite of its widespread use, sodium bicarbonate can be harmful in large doses by disrupting the levels of sodium ions in the bloodstream. In a few rare cases, some people have consumed such large amounts of sodium bicarbonate that their stomachs were damaged by the internal pressure that built up from the carbon dioxide gas.