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A base is a chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. Bases and acids are referred to as opposites because the effect of an acid is to increase the hydronium ion concentration in water, whereas bases reduce this concentration. Inorganic bases are typically water-soluble and always have a pH greater than 7 in solution.

1 Common bases

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

2 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 hydrogen ions (H⁺) and hydroxide ions (OH⁻), according to the equation

The concentration (in moleThe mole (symbol: mol) is one of the seven SI base units and is commonly used in chemistry. It measures the amount of substance of a system and is defined as the amount of substance that contains as many elementary entities as there are atoms in exactly 0/ literThe litre (or liter in US) is a metric unit of volume. The litre is not an SI unit, but is "accepted for use with the International System". The symbol for the litre is the lowercase letter l or the uppercase letter L . A cursive or script small letter l) of the ions is indicated as [H⁺] and [OH⁻]; their product is the dissociation constantIn chemistry and biochemistry the dissociation constant abbreviated K is a measure of the extent to which a dissociation reaction :AB ↔ A + B proceeds at equilibrium. It is given quantitatively by the expression K [A]×[B]×[AB]-1 Where [A], [B], and [ 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) hydrogen ions (H⁺) from the solution, or donates hydroxide ions (OH⁻) to the solution. Both actions will lower the concentration of hydrogen ions, 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 hydroxideSodium hydroxide ( Na OH), also known as caustic soda or lye in North America, is a caustic metallic base used in industry (mostly as a strong chemical base) in the manufacture of paper, textiles, and detergents. Sodium hydroxide is occasionally used in t (40 gG is the seventh letter in the Roman alphabet. History The letter G was created by the Romans because they felt that C was not an adequate letter to represent both /k/ and /g/. Fascinatingly, the alleged inventor is a known historical figure, Spurius Carv) is dissolved in 1 liter of water, the concentration of hydroxide ions becomes [OH⁻] = 1 mole/l. Therefore [H⁺] = 10⁻¹⁴ mol/l, and pH = −log 10⁻¹⁴ = 14.