D.2+Antacids

=D.2 Antacids = D.2.1 State and explain how excess acidity in the stomach can be reduced by the uses of different bases
 * 

 Antacids** //-// bases that neutralize the excess acidity and relieve the pain associated with heartburn and peptic ulcers.

Common antacids are oxides or hydroxides of aluminum (aluminum hydroxide, aluminum oxide), magnesium (magnesium hydroxide, magnesium oxide), or calcium (calcium hydroxide, calcium oxide, calcium carbonate). Sometimes sodium hydrogen carbonate (NaHCO3) is also used.

The reaction of stomach acid, hydrochloric acid (HCl), with an antacid is an example of an acid-base / neutralization reaction (see topic 8.2).Generalized reactions: acid + base → salt + water or if the antacid is a metal carbonate acid + base → salt + water + carbon dioxide gas

Examples:

__Aluminum hydroxide:__


 * most effective, since for every 1 mole of aluminum hydroxide used, 3 moles of hydrochloric acid are neutralized. (Molar ratio 1:3)

__Magnesium hydroxide__:

Magnesium hydroxide is faster acting, but since aluminum hydroxide dissolve more slowly, it tends to provide longer lasting relief. I mole of magnesium hydroxide neutralizes 2 moles of hydrochloric acid.

__Sodium hydrogencarbonate:__

1 moles of sodium hydrogen carbonate neutralizes 1 mole of hydrochloric acid.

__Calcium carbonate:__ I mole of calcium carbonate neutralizes 2 moles of hydrochloric acid.

Antacids are all weak bases. Strong bases like sodium hydroxide or other group 1 metal hydroxides are are not used because they are corrosive to body tissue.

When the antacid is a metal carbonate, carbon dioxide gas is produced which can cause vomiting. In order to avert this, antifoaming agents and alginates (like dimethicone) are added.


 * Alginates**
 * polymers that are derived from brown seaweeds.
 * They float on top of the stomach contents, providing a neutralizing layer that acts as a barrier preventing stomach acid from rising up into the esophagus (called heartburn - pain in the chest).


 * Anti foaming agents**
 * prevent bloating and flatulance (burping)

Brown, Catrin and Mike Ford. __Standard Level Chemistry__. UK: Heinnemann Baccalaureate, 2008. Derry, Lanna, et al. __Chemistry for use with the IB Diploma Options Course Book__. Melbourne: Pearson Heinemann, 2009.
 * Works Cited:**