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Acids and Bases |
Robert Boyle in the seventeenth century first identified substances as either acids or bases (he called bases alkalis) according to the following characteristics:
Bases also damage protein . This results in the "slippery" feeling on hands
when exposed to base. Strong bases that dissolve well in water , such as
sodium or potassium lye are very dangerous because a great amount of the structural
material of human beings is made of protein.
When a base is mixed with an acid the acidity is reduced and vice versa. This is called
As you can see above, acids release H+ into solution and bases release OH-.
If we were to mix an acid and base together, the H+ ion would combine with the OH- ion to make the molecule H2O, or plain water:
The modern definition of Acids and Bases is based on Johannes Brønsted's and
Thomas Lowry's versions both definitions were published in the early 1920's
and were similar. Acids and bases are defined in accordance with
Brønsted-Lowry as follows.
A salt is the combination of an anion (- ion) and a cation (a + ion) ( ref Ions and cations).
A salt results from the combination of the anion of a certain acid
combined with the cation of a certain base. The neutralization of
potassium hydroxide with hydrochloric acid produces water and the salt, potassium
chloride. In a solid salt, the ions are held together by the difference
in charge. Solid salts generally form crystals,
posssible including specific amounts of water, called water of hydration into the crystal.
If a salt dissolves in water solution, it normally separates into the anions
and cations that make up the salt.
The common acids that are almost one hundred percent ionized are:
The acids on this short list are called strong acids, because the amount of acid
quality of a solution depends upon the concentration of ionized hydrogens.
Other acids are incompletely ionized, existing mostly as the unionized form.
Incompletely ionized acids are called weak acids, because there is a smaller concentration of
ionized hydrogens available in the solution. Strong and weak acids are not the
same as dilute and concentrated acids.
The differences in concentration of the entire acid will be termed dilute or concentrated. Muriatic acid is the name given to an industrial grade of hydrochloric acid that is often used in the finishing of concrete.
This is a short list of strong bases i.e ones that completely ionize into hydroxide ions
and a conjugate acid. All of the bases of Periodic Table Group I and Group II
metals except for beryllium are strong bases. The bases of Group II metals,
magnesium, calcium, barium, and strontium are strong, but all of these bases have
somewhat limited solubility. Magnesium hydroxide has a particularly small
Hydrogen ion concentrations are measured as the number of gram ions of hydrogen present per litre
of solution. Since these concentrations are usually small the concentration is generally
expressed as the pH of the solution: the pH being the logarithm i.e pH = - log[H+]. The pH can be
measured using a glass electrode or less accurately using coloured indicators...
Table identifying Acids/Bases
|Links relevant Acids and Bases..||
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Last Updated 28/01/2013