Buffer Solutions The Control of pH

Hydrolysis is the term used for the general reaction in which a water molecule is split. For example, the net ionic hydrolysis reaction for a sodium acetate solution is 

In this reaction the water molecule is split, with the combining with C2H3O2 to give the weak acid HC2H3O2 and the OH going into solution, making the solution more basic. 

Salts that contain an ion of a weak acid undergo hydrolysis. For example, a 0.10 M NaCN solution has a pH of 11.1. The hydrolysis reaction that causes this solution to be basic is 

If a salt contains the ion of a weak base, the ion produces an acidic solution by transferring a proton to water. An example is ammonium chloride, which produces the NH4 and Cl in solution. The NH4 hydrolyzes to give an acidic solution  

The ions of a salt derived from a strong acid and a strong base, such as NaCl, do not undergo hydrolysis and thus form neutral solutions. Table 16.4 lists the ionic composition of various salts and the nature of the aqueous solutions that they form. 

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