This MedLibrary.org supplementary page on Weak acid is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
- Acid dissociation constant
- Acid-base extraction
- Acid-base reaction
- Acid-base physiology
- Acid-base homeostasis
- Dissociation constant
- Acidity function
- Buffer solutions
- pH
- Proton affinity
- Self-ionization of water
- Acids:
- Lewis acids
- Mineral acids
- Organic acids
- Strong acids
- Superacids
- Weak acids
- Bases:
A weak acid is an acid that dissociates incompletely and does not release all of its hydrogens in a solution. It does not donate all of its hydrogens. These acids have higher pKa compared to strong acids, which release all of their hydrogens when dissolved in water.
While strong acids are generally assumed to be the most corrosive, this is not always true. The carborane superacid (H(CHB11Cl11), which is one million times stronger than sulfuric acid, is entirely non-corrosive, whereas the weak acid hydrofluoric acid (HF) is extremely corrosive and can dissolve, among other things, glass and all metals except iridium.
Explanation
Weak acids do not 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
The equilibrium concentrations of reactants and products are related by the Acidity constant expression, (Ka):
![\mathrm{ K_a\, =\, \frac {[H^+\,][A^-\,]}{[HA]} }](http://upload.wikimedia.org/math/e/1/1/e1160cb29e6e647fa04612aee2af4f35.png)
The greater the value of Ka, the more the formation of H+ is favored, and the lower the pH of the solution. The Ka of weak acids varies between 1.8×10-16 and 55.5. Acids with a Ka less than 1.8×10-16 are weaker acids than water. Acids with a Ka of greater than 55.5 are strong acids and almost totally dissociate when dissolved in water.
Examples
The vast majority of acids are weak acids. Organic acids are a large subset of weak acids. However, there are some mineral acids in this field.
See also
Wikipedia content modification information:
- This page was last modified on 20 November 2008, at 09:57.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Weak acid".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.