The Behavior of Polyprotic Acids

Acids with more than one ionizable proton are polyprotic acids. In a solution of a polyprotic acid, one proton at a time dissociates from the acid molecule, and each dissociation step has a different K. For example, phosphoric acid is a tripro-tic acid (three ionizable protons), so it has three values  

Two common types of weak-acid equilibrium problems involve finding Kg from a concentration and finding a concentration from Kg. We summarize the information in a reaction table, and we simplify the arithmetic by assuming (1) is so 

5 WEAK BASES AND THEIR RELATION TO WEAK ACIDS 

By focusing on where the proton comes from and goes to, the Brpnsted-Lowry concept expands the definition of a base to encompass a host of species that the Arrhenius definition excludes a base is any species that accepts a proton to do so, the base must have a lone electron pair. (The lone electron pair also plays the central role in the Lewis acid-base definition, as you ll see later in this chapter.) 

Now let s examine the equilibrium system of a weak base and focus, as we did for weak acids, on the base (B) dissolving in water. When B dissolves, it accepts a proton from H2O, which acts as an acid, leaving behind an OH ion  

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