Base (chemistry)

Acids and Bases:

Acid-base reaction theories

Self-ionization of water

Buffers

Systematic_naming

Redox reactions

Electrochemistry

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

baking soda
sodium carbonate
ammonia
Many metal oxides and hydroxides will also form basic solutions.

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