Strong acid

Strong acid

A strong acid is an acid that ionizes completely in an aqueous solution (not in the case of sulfuric acid as it is diprotic), or in other terms, with a p"K"a < −1.74. This generally means that in aqueous solution at standard temperature and pressure, the concentration of hydronium ions is equal to the concentration of strong acid introduced to the solution. 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. The equation for complete dissociation of an acid in aqueous solution is as follows:

:HA(aq) → H+(aq) + A(aq)

In all other acid-water reactions, dissociation is not complete, so will be represented as an equilibrium, not a completed reaction. The typical definition of a weak acid is any acid that does not dissociate completely. The difference separating the acid dissociation constants of strong acids from all other acids is so small that this is a reasonable demarcation.

Due to the complete dissociation of strong acids in aqueous solution, the concentration of hydronium ions in the water is equal to the re-duplication of the acid introduced to solution: [HA] = [H+] = [A] ; pH = −log [H+] .

Determining acid strength

The strength of an acid, in comparison to other acids, can be determined without the use of pH calculations by observing the following characteristics:

# Electronegativity: The higher the EN of a conjugate base in the same period, the more acidic.
# Atomic Radius: With increasing atomic radius, acidity also increases. For example, HCl and HI, both strong acids, ionize 100% in water to become their respective ionic constituents. However, HI is stronger than HCl. This is because the atomic radius of an atom of iodine is much larger than that of a chlorine atom. As a result, the negative charge over the I- anion is dispersed over a larger electron cloud and its attraction for the proton (H+) is not as strong as the same attraction in HCl. Therefore, HI is ionized (deprotonated) more readily.
# Charge: The more positively charged a species is, the more acidic (neutral molecules can be stripped of protons more easily than anions, and cations are more acidic than comparable molecules).

ome common strong acids (as ionizers)

(Strongest to the weakest)

* Perchloric acid HClO4
* Hydroiodic acid HI
* Hydrobromic acid HBr
* Hydrochloric acid HCl
* Sulfuric acid H2SO4 ("K"a1/first dissociation only)
* Nitric acid HNO3
* Hydronium ion H3O+ or H+. For purposes of simplicity, H3O+ is often replaced in a chemical equation with H+. However, it should be noted that a bare proton simply does not exist in water but instead is bound to one of the lone pairs of electrons on the H2O molecule. This creates the hydronium ion and gives its single O atom a formal charge of +1.

* Some chemists include chloric acid (HClO3), bromic acid (HBrO3), perbromic acid (HBrO4), iodic acid (HIO3), and periodic acid (HIO4) as strong acids, although these are not universally accepted.

Extremely strong acids (as ionizers)

(Strongest to weakest)
* Fluoroantimonic acid HFSbF5
* Magic acid FSO3HSbF5
* Carborane superacid H(CHB11Cl11)
* Fluorosulfuric acid FSO3H
* Triflic acid CF3SO3H

ee also

* Strong base
* Weak acid


*Hill, John W., et al. "General Chemistry." 4th ed. New Jersey: Prentice Hall, 2005.

External links

* Titration of acids [ - freeware for data analysis and simulation of potentiometric titration curves]
* Acids and Bases [ - definitions]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • strong acid — stiprioji rūgštis statusas T sritis chemija apibrėžtis Rūgštis, praskiestame tirpale visiškai disocijuojanti į jonus. atitikmenys: angl. strong acid rus. сильная кислота …   Chemijos terminų aiškinamasis žodynas

  • strong acid — acid which contains components of a high concentration …   English contemporary dictionary

  • strong´ness — strong «strng, strong», adjective, strong|er«STRNG guhr, STRONG »,strong|est«STRNG guhst, STRONG », adverb. –adj. 1. a) having much force or power: »strong arms, a strong army. A strong man can lift heavy things. A strong wind blew down the trees …   Useful english dictionary

  • strong´ly — strong «strng, strong», adjective, strong|er«STRNG guhr, STRONG »,strong|est«STRNG guhst, STRONG », adverb. –adj. 1. a) having much force or power: »strong arms, a strong army. A strong man can lift heavy things. A strong wind blew down the trees …   Useful english dictionary

  • Strong — may refer to:General usage*Strong acid *Strong agnosticism *Strong AI *Strong atheism *Strong cardinal *Strong coloring *Strong convergence *Strong CP problem *Strong cryptography *Strong inflection (linguistics):*Germanic strong verb *Strong… …   Wikipedia

  • Acid dissociation constant — Acetic acid, a weak acid, donates a proton (hydrogen ion, high …   Wikipedia

  • Acid — This article is about acids in chemistry. For the drug, see Lysergic acid diethylamide. For other uses, see Acid (disambiguation). Acidity redirects here. For the novelette, see Acidity (Novelette). Acids and Bases …   Wikipedia

  • acid–base reaction — ▪ chemistry Introduction       a type of chemical process typified by the exchange of one or more hydrogen ions, H+, between species that may be neutral (molecules, such as water, H2O; or acetic acid, CH3CO2H) or electrically charged (ions, such… …   Universalium

  • Acid–base reaction — An acid base reaction is a chemical reaction that occurs between an acid and a base. Several concepts exist which provide alternative definitions for the reaction mechanisms involved and their application in solving related problems. Despite… …   Wikipedia

  • Acid-base titration — [ frame|100px|frame|Titration setup. The burette would normally be held by a clamp, not shown here. The pink is most likely caused by use of the phenolphthalein indicator.] An acid base titration is a method in chemistry that allows quantitative… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.