The values of equilibrium constants for strong acids are indeed very large, and this indicates that they dissociate almost completely in solution. For example, hydrochloric acid (HCl) has a Ka value of about 1.3 x 106, or 1,300,000, meaning it releases a significant amount of hydrogen ions (H+) when dissolved in water.
In contrast, weak acids do not dissociate completely. They only partially ionize in solution, leading to smaller Ka values. However, it’s important to clarify the question: Ka values for weak acids are typically much smaller than those for strong acids. Thus, when we see some weak acids with relatively larger Ka values, it simply means they are more dissociated than other weak acids but still less than strong acids.
For instance, acetic acid is a commonly referenced weak acid with a Ka of about 1.8 x 10-5, which indicates that it doesn’t dissociate as fully as hydrochloric acid. The reason why weak acids have lower Ka values compared to strong acids is due to the strength of the bond between the hydrogen atom and the rest of the acid molecule. Strong acids, with their weaker H-A bond, break apart more readily in water, while weak acids have stronger bonds that resist dissociation.