The question then arises, and how to calculate the acidity of solutions of weak acids. In fact, because if the acid dissociates completely, then how do we know which molecules dissociate and what is not.
Thus, we come to the concept of the acidity constant. Assume that there is a weak acid HA, which dissociates into H + ion and A -. Based on the fact that we have a weak acid and it dissociates completely, we understand that at some point we have to establish some form of concentration of the undissociated acid and ions. We call such a concentration equilibrium. Suppose that the equilibrium concentration of protons is x, then the equilibrium concentration of the anions of acidic residues is also equal to x. The equilibrium concentration of the acid is equal to the difference between the initial concentration of acid (e.g. C 0) and the concentration of dissociated molecules (i.e., x). The ratio of x * x / (C 0 -x) called constant acidity. These data are presented in different tables. How to use them in the calculation of pH - the next time