The second buffer region

This will be handled either by the more approximate method, or by the more rigorous method of successive approximations. In general, the more rigorous method will have to be used the closer the titration is to the first equivalence point. For most of the buffer region away from the first equivalence point, the more approximate series of successive approximations should be adequate. 

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At point C, the system is in the second buffer region and pH = pKa2- Enough base takes us to the second stoichiometric point, D. The primary species in solution are now the monoprotic anions HP042 and sodium ions, which form a solution of... 

Moving beyond the first stoichiometric point, the titration enters the second buffer region. Here, the major species are H A and its conjugate base,. The pH in this region is given by the buffer equation, using the p of H j4.". At the second midpoint, [H j4" ] = [j4 " ], and pH = p. Ta 2 For the titration of maleic acid, pH = 6.59 at the second midpoint. 

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