Base is any substance that in aqueous solution undergoes ionic dissociation, releasing the OH anion- (Hydroxide).
Ionic dissociation is related to the behavior of bases in the presence of water. Example: caustic soda (NaOH) is a solid substance that in contact with water releases Na ions+ and oh- which dissolve due to the attraction of the negative and positive poles of the H molecule2O. Thus, bases are substances composed by the combination of a cation (usually a metal) with the OH anion-.
One of the characteristics of the bases is their astringent taste, which “binds” the mouth, that is, it reduces salivation.
Like acids, bases also conduct electrical current when dissolved in water. The phenolphthalein (solution) and litmus paper indicators also change color in the presence of hydroxides. Colorless phenolphthalein turns red; red litmus paper turns blue: reverse reactions to those seen in the case of acids.
Let's see the main bases:
Sodium Hydroxide (NaOH): Also known as caustic soda, this substance is used in the manufacture of soap, cellophane, detergents and rayon, products to unclog sinks and drains, and also in the pulp extraction process in the paper industries, etc.
Magnesium Hydroxide (Mg(OH)2): It is present in the solution that is marketed under the name “milk of magnesia”, a product used as a laxative and stomach antacid.
Calcium hydroxide (Ca(OH)2): Known as hydrated lime or quenched lime, this substance is used in civil construction: in the preparation of mortar (sand + lime) and in whitewashing (lime painting); the sugar industries used calcium hydroxide to purify common sugar.
Ammonium hydroxide (NH4OH): This substance is obtained in an aqueous solution of ammonia gas and sold as ammonia. It is used in the manufacture of household cleaning products, in photographic film development, in detergents, in the textile industry, etc.
Potassium hydroxide (KOH): Known as caustic potash, it is used for bleaching, in the manufacture of soft soaps, and in the processing of certain foods.
By Líria Alves
Graduated in Chemistry
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Would you like to reference this text in a school or academic work? Look:
SOUZA, Líria Alves de. "Bases"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/bases.htm. Accessed on June 27, 2021.
