Base is any substance that produces the OH- (hydroxyl) anion in water. When a base comes in contact with water, it dissociates and releases OH-. Examples:
NaOH + H2O ↔ Na + + OH-
Mg (OH)2 + H2O ↔ Mg2+ + 2OH-
Al (OH)3 + H2O ↔ Al3+ + 3OH-
A base is identified by the presence of OH- on the right side of the formula. The main features of the bases are:
- astringent taste (taste like that of green banana that seems to “hold” the tongue);
- conduct electricity in aqueous solution (in water);
- change the color of certain substances, the so-called acid-base indicators;
-reaction with acids forming salt and water.
- Sodium hydroxide (NaOH) - also known as caustic soda. It is toxic and corrosive. Used to unclog sinks. It is widely used in the chemical industry to prepare soap and other organic compounds.
- Magnesium hydroxide (Mg (OH)2) - used as stomach antacid. It is also called milk of magnesia.
- Calcium hydroxide - (Ca (OH)2) - called hydrated lime, unlit lime, or extinct lime. Used in construction to prepare mortar and used in paintings. Calcium hydroxide in water is called lime milk or lime water.
- Ammonium hydroxide (NH4OH) in aqueous solution is known as ammonia or ammonia. Used in home cleaning, fat and oil saponification. It is toxic and irritating to the eyes.