Base (chemistry)
All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century.
In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form hydroxide ions OH−.
They are slippery to the touch, can taste bitter[1] and change the color of pH indicators (e.g., turn red litmus paper blue).
However, there are also other Brønsted bases which accept protons, such as aqueous solutions of ammonia (NH3) or its organic derivatives (amines).
[7] When dissolved in water, the strong base sodium hydroxide ionizes into hydroxide and sodium ions: and similarly, in water the acid hydrogen chloride forms hydronium and chloride ions: When the two solutions are mixed, the H3O+ and OH− ions combine to form water molecules: If equal quantities of NaOH and HCl are dissolved, the base and the acid neutralize exactly, leaving only NaCl, effectively table salt, in solution.
Weak bases, such as baking soda or egg white, should be used to neutralize any acid spills.
Both compounds accept H+ when dissolved in protic solvents such as water: From this, a pH, or acidity, can be calculated for aqueous solutions of bases.
[7] There are a limited number of elements that have atoms with the ability to provide a molecule with basic properties.
A strong base is a basic chemical compound that can remove a proton (H+) from (or deprotonate) a molecule of even a very weak acid (such as water) in an acid–base reaction.
[9] As the reaction continues and the salts dissolve, the stomach acid reacts with the hydroxide produced by the suspensions.
Group 1 salts of carbanions, amide ions, and hydrides tend to be even stronger bases due to the extreme weakness of their conjugate acids, which are stable hydrocarbons, amines, and dihydrogen.
Usually, these bases are created by adding pure alkali metals such as sodium into the conjugate acid.
They are called superbases, and it is impossible to keep them in aqueous solutions because they are stronger bases than the hydroxide ion (See the leveling effect.)
For example, the ethoxide ion (conjugate base of ethanol) undergoes this reaction quantitatively in presence of water.
In addition to H+, possible electron-pair acceptors (Lewis acids) include neutral molecules such as BF3 and high oxidation state metal ions such as Ag2+, Fe3+ and Mn7+.
Basic catalysts are used for hydrogenation, the migration of double bonds, in the Meerwein-Ponndorf-Verley reduction, the Michael reaction, and many others.
[15] Bases with only one ionizable hydroxide (OH−) ion per formula unit are called monoprotic since they can accept one proton (H+).
In keeping with 16th-century animism, Paracelsus had postulated that naturally occurring salts grew within the earth as a result of a universal acid or seminal principle having impregnated an earthy matrix or womb.
... Its modern meaning and general introduction into the chemical vocabulary, however, is usually attributed to the French chemist, Guillaume-François Rouelle.
In 1754 Rouelle explicitly defined a neutral salt as the product formed by the union of an acid with any substance, be it a water-soluble alkali, a volatile alkali, an absorbent earth, a metal, or an oil, capable of serving as "a base" for the salt "by giving it a concrete or solid form."
Most acids known in the 18th century were volatile liquids or "spirits" capable of distillation, whereas salts, by their very nature, were crystalline solids.
