Acid Dissociation Constant (Ka)
The acid dissociation constant (Ka) quantifies the strength of an acid in solution. It is defined as the equilibrium constant for the dissociation of the acid into its conjugate base and a proton. For aspirin, with a Ka of 3.0 x 10^-4, this value indicates that it is a weak acid, and it helps in calculating the concentration of hydrogen ions in solution, which is crucial for determining pH.