Acid dissociation constant (Ka) for weak acids and pKa

Ka values reflect how strong or weak an acid is. Strong acids have higher Ka values, since they have more impact on the proton concentration. On the other hand, weak acids have lower Ka values, and we can compare these values between acids to say which ones are stronger or weaker. For instance, by watching the Ka values of acetic and phosphoric acid, we can be sure that the phosphoric acid is the stronger of the two. Ka values have concentration units, and tend to be large numbers to read and compare. For simplicity, if we take the negative logarithm of this number we obtain a new value called pKa, similar to pH, which is the negative logarithm of proton concentration.