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Acid, Acidic and Acidity
- An Acid is a compound able to release hydrogen ions (H+) in solution.
As an example, hydrochloric acid (HCl) is able to release hydrogen ions
(H+) when it disassociates in solution as shown in the expression below.
HCl <==> Cl- + H+
- An acidic solution is a solution with an excess of free hydrogen ions (H+)
- Acidity in wine can be detected on the sides of our tongues as a sour taste, a tingling sensation or a sharp, bitting almost painful sensation when in excess.
Warning - Do not taste acidic solutions as they can lead to extreme acid burns to the mouth and internal organs.
- The acidity of a solution depends on -
- Total acidity, titratable acidity and pH, although related do not measure the same aspect of acidity.
Base, basic or alkalinity
- The oposite to an acid, acidic or acidity is a base, basic or alkalinity respectively.
- A base is a compound able to release hydroxide ions (OH-) in solution.
As an example, the basic compound sodium hydroxide (NaOH) disassociates in solution to release hydroxide ions (OH-) as shown in the expression below.
NaOH <==> Na+ + OH-
- Similarly, compounds able to bind hydrogen ions (H+), with a reduction in the solution's acidity, and hence an increase in alkalinity, are also bases.
As an example, when hydrochloric acid (HCl) disassociates in solution to release hydrogen ions (H+) and chloride ions (Cl-) as shown in the expression below, the double headed arrow
indicates that the Cl- can act as a base by recombining with the H+.
HCL <==> Cl- + H+
- A basic or alkaline solution is a solution with an excess of hydroxide ions (OH-).
- A hydroxide ion (OH-) will react with one hydrogen ion (H+) to form one molecule of water (H2O)