How does equilibrium affect the strength of an acid?
1 Answer
Effect of equilibrium
One of the ways of determining the strength of an acid is its pKa value.
Any acid will dissociate in the following manner
And
The larger the value of pKa, the smaller the extent of dissociation at any given pH—that is, the weaker the acid. A weak acid has a pKa value in the approximate range −2 to 12 in water. Acids with a pKa value of less than about −2 are said to be strong acids; a strong acid is almost completely dissociated in aqueous solution, to the extent that the concentration of the undissociated acid becomes undetectable. In other words the denominator of the above equation is so small that the value of
Weak acids have considerably high concentrations of molecules that are not dissociated. Hence the value of
pKa values for strong acids can, however, be estimated by theoretical means or by extrapolating from measurements in non-aqueous solvents in which the dissociation constant is smaller, such as acetonitrile and dimethylsulfoxide.
Source:Acid Dissociation