Acid strength

Acid strength is the tendency of an <a href="/facts/Acid/FySU18n1">acid</a>, symbolised by the <a href="/facts/Chemical_formula/hghUtthl">chemical formula</a> HA, to dissociate into a <a href="/facts/Hydron_(chemistry)/v5Qkumvm">proton</a>, H+, and an <a href="/facts/Anion/wrbwhF3z">anion</a>, A−. The <a href="/facts/Dissociation_(chemistry)/gDRGdeSN">dissociation</a> or <a href="/facts/Ionization/W13Ceavd">ionization</a> of a strong acid in solution is effectively complete, except in its most concentrated solutions.

HA → H+ + A−
Examples of <a href="/facts/Strong_acid/vJ4rj6Lu">strong acids</a> are <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a> (HCl), <a href="/facts/Perchloric_acid/gjhK386J">perchloric acid</a> (HClO4), <a href="/facts/Nitric_acid/UDbwGp6s">nitric acid</a> (HNO3) and <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> (H2SO4).
A weak acid is only partially dissociated, or is partly ionized in water with both the undissociated acid and its dissociation products being present, in solution, in <a href="/facts/Equilibrium_chemistry/mkjCWwnx">equilibrium</a> with each other.

HA ⇌ H+ + A−
<a href="/facts/Acetic_acid/uyBKA2Pd">Acetic acid</a> (CH3COOH) is an example of a weak acid. The strength of a weak acid is quantified by its <a href="/facts/Acid_dissociation_constant/t4YyRtKC">acid dissociation constant</a>, 
 
 
 
 
 K
 
 a
 
 
 
 
 {\displaystyle K_{a}}
 
 value.
The strength of a weak <a href="/facts/Organic_chemistry/djxhxaNg">organic</a> acid may depend on substituent effects. The strength of an <a href="/facts/Inorganic_chemistry/ErD6ypnb">inorganic</a> acid is dependent on the <a href="/facts/Oxidation_state/W53W6s6V">oxidation state</a> for the atom to which the proton may be attached. Acid strength is solvent-dependent. For example, <a href="/facts/Hydrogen_chloride/7Wzkhomd">hydrogen chloride</a> is a strong acid in aqueous solution, but is a weak acid when dissolved in <a href="/facts/Glacial_acetic_acid/uyBKA2Pd">glacial acetic acid</a>.

Acid strength open-in-new

Acid strength