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Base (chemistry)
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Base (chemistry)

Acids and Bases:
Acid-base reaction theories
Self-ionization of water
Redox reactions
Strong acids
Weak acids
Weak bases
Strong bases

A base is a chemical compound that will neutralize an acid and form a salt + water. Bases are typically water-soluble and bitter tasting and always have a pH greater than 7 in solution. A base is able to take up a proton from an acid or able to give up an unshared pair of electrons to an acid.

Table of contents
1 Common bases
2 Bases and pH
3 Neutralization of acids
4 Alkalinity of non-hydroxides
5 Theorys of Bases
6 See also

Common bases

Bases and pH

The pH of (impure) water is a measure of its acidity. In pure water, about one in ten million molecules dissociate into hydronium ionss (H+) and hydroxyl ionss (OH), according to the equation

The concentration (in mole/liter) of the ions is indicated as [H+] and [OH]; their product is the dissociation constant of water with and has the value 10−14 mole2/l2. The pH is defined as −log [H+]; thus, pure water has a pH of 7. (These numbers are correct at 23 °C and slightly different at other temperatures.)

A base accepts (removes) hydronium ionss (H+) from the solution, or donates hydroxyl ionss (OH) to the solution. Both actions will lower the hydronium concentration, and thus raise pH. By contrast, an acid donates H+ ions to the solution or accepts OH, thus lowering pH.

The pH of a solution can be calculated. For example, if 1 mole of sodium hydroxide (40 g) is dissolved in 1 liter of water, the concentration of hydroxyl ions becomes [OH] = 1 mole/l. Therefore [H+] = 10−14 mol/l, and pH = −log 10−14 = 14.

Neutralization of acids

When dissolved in water, sodium hydroxide decomposes into hydroxyl and sodium ions:

and similarly, hydrochloric acid forms hydronium and chloride ions:
When the two solutions are mixed, the H+ and OH ions combine to form water molecules:
If equal amounts of NaOH and HCl (measured in moles, not grams) are dissolved, the base and the acid exactly neutralize, leaving only NaCl (table salt) in solution.

Alkalinity of non-hydroxides

Both sodium carbonate and ammonia are bases, although neither of these substances contains OH groups. That is because both compounds accept H+ when dissolved in water:

Theorys of Bases

Arrhenius Bases

A compound that gives hydroxide ions in an aqueous solution

Bronsted - Lowey Base

A proton acceptor

Lewis Base

Electron pair donor

See also