What Is the Ka of HCl?

The acid dissociation constant, or Ka, is a way of ranking the strength of acids. Acids with lower Ka values are called weak acids. These acids dissociate only partially. Examples of weak acids are acetic acid (vinegar), ascorbic acid (vitamin C) and formic acid.

Polyprotic acids can lose more than one proton. These acids have Ka values for the loss of each proton. In general, the Ka reduces as each successive proton is lost.