Weak acid
166506
223519498
2008-07-04T12:32:47Z
122.53.239.140
/* Explanation */
{{Acids_and_Bases}}
A '''weak acid''' is an [[acid]] that does not completely donate all of its hydrogens when dissolved in water. These acids have higher [[pH]] compared to [[strong acids]], which release all of their hydrogens when dissolved in water.
==Explanation==
Weak acids do not [[ionization|ionize]] in a [[solution]] to a significant extent; that is, if the acid was represented by the general formula ''HA'', then in aqueous solution a significant amount of undissociated HA still remains. Weak acids in water dissociate as
<math>\mathrm{ HA_{(aq)} \, \leftrightarrow \, H^+\,_{(aq)} +\, A^-\,_{(aq)} }.</math>
The equilibrium concentrations of reactants and products are related by the [[Acidity constant]] expression, (K<sub>a</sub>):
<math>\mathrm{ K_a\, =\, \frac {[H^+\,][A^-\,]}{[HA]} }</math>
The greater the value of K<sub>a</sub>, the more the formation of H<sup>+</sup> is favored, and the lower the [[pH]] of the solution. The K<sub>a</sub> of weak acids varies between 1.8×10<sup>-16</sup> and 55.5. Acids with a K<sub>a</sub> less than 1.8×10<sup>-16</sup> are weaker acids than water. Acids with a K<sub>a</sub> of greater than 55.5 are [[strong acids]] and almost totally dissociate when dissolved in water and sea level magnitude
==Examples==
The vast majority of acids are weak acids. Organic acids are a large subset of weak acids. However, there are some [[mineral acid]]s in this field.
*[[acetic acid]]
*[[citric acid]]
*[[boric acid]]
*[[phosphoric acid]]
*[[hydrofluoric acid]]
==See also==
* [[Strong acid]]
* [[Weak base]]
[[Category:Acids]]
[[es:Ácido débil]]
[[fr:Acide faible]]
[[hr:Slaba kiselina]]
[[id:Asam lemah]]
[[it:Acidi deboli]]
[[nl:Zwak zuur]]
[[fi:Heikko happo]]
[[sv:Svag syra]]
[[zh:弱酸]]