Hydrochloric Acid
A highly corrosive and strong mineral acid, hydrochloric acid is the result of taking a hydrogen chloride solution and added it into water. Hydrochloric acid has considerable industrial uses. More importantly to humans, though, is the fact that it is naturally found within our bodies in gastric acid. With an incredibly high molarity (strength of an acid), the hydrochloric acid is able to kill most bacteria that might come into the body when eating food. This is one of the body’s methods of ensuring that the body does not get sick from eating different types of foods.
History of Hydrochloric Acid
Hydrochloric acid (HCl) was first discovered around the year 800 C.E. It was discovered by an alchemist named Jabir ibn Hayyan. By mixing salt with sulfuric acid, he was able to discover numerous important chemical. He recorded this information in over twenty different books, all carrying knowledge about different acids and bases.
In the Middle Ages, alchemists used hydrochloric acid because they felt it would help them on their quest for the philosopher’s stone. The philosopher’s stone is a mythological stone that can turn lead into gold. Since then, it has had numerous other uses throughout the years. Because of the ease in which it is created and the strength of the acid, it is a favorite for numerous different applications.
Chemistry of HCl
Hydrochloric acid is a monoprotic acid. This means it can only dissociate once to give up a single hydrogen ion. When the acid is put into water, the hydrogen ion breaks off of the HCl and attaches to the water. This creates a hydronium ion. It looks similar to water, but it possesses three hydrogen, not two. It looks like this:
HCl + H2O –> H3O(+) + Cl(-)
Because HCl is a strong acid, it completely dissociates. This means that once the water and the acid are mixed, it breaks apart into the hydronium ion and the chloride ion. It won’t go back to being water and HCl naturally. This differs from weak acids because they consistently go back and forth between their ionic stages and their combined stages.
Hydrochloric Acid in the Body
Chloride and Hydrogen ions are kept separately in the stomach fundus region. The two ions, specifically, are held by parietal cells found in the gastric mucosa. When someone eats food, these ions are released together and combine to form the incredibly strong acid. The pH of the stomach contents can be between 1 and 2 which is immensely acidic. Not only does the HCl kill microorganisms that are trying to do harm, it also plays a key part in the digestion of food. Because of the low pH, the protions in the food denature which allows the digestive enzyme pepsin to degrade it further.
The big thing people ask, then, is why doesn’t the stomach get damaged from the HCl? Another question is why doesn’t the intestine get damaged after the food leaves the stomach?
The stomach is protected because it is consistently secreted a thick mucus layer. As the acid eats away at the layer, more mucus is released and therefore, it never does any damage to the stomach. However, heart burn is the feeling of some of this acid going up the esophagus. Therefore, taking an acid reflux such as Tums is an effective way of controlling the acid.
The reason the acid doesn’t hurt the intestines when the food leaves is because the chyme (the food when leaving the stomach) is neutralized in the duodenum by sodium bicarbonate. Sodium bicarbonate is a strong base and therefore, neutralizes the hydrochloric acid and allows the chyme to move into the intestines to be processed. The equation of hydrochloric acid being neutralized by sodium bicarbonate looks like this:
HCl + NaHCO3 –> NaCl + H2O + CO2.