How does Ka relate to acid strength?

1 Answer
Aug 1, 2016

Strong acids typically possess large Ka values.

Explanation:

The generalized protonolysis reaction for an acid in water is as follows:

HX(aq)+H2O(l)H3O++X

And of course Ka=[H3O+][X][HX]

For strong acids, i.e. HX,H2SO4.HClO4, the equilibrium lies almost quantitatively to the RIGHT. Given this we can look back to the the Ka expression and realize that if equilibrium quantities of [H3O+] and [X] are large and [HX] is small, then Ka is correspondingly large. And thus large Ka values betoken strong acids.