Buffer capacity monoprotic acids

One can now determine the pH at which a weak monoprotic acid exhibits its maximum buffer capacity (yS ,ax). This involves differentiating Eq. (5.111) with respect to pH and then setting the expression for djSIdpH equal to zero. This leads to K = [HT for the condition of maximum buffer capacity. Substituting this fact into Eq. (5.111) indicates that... 

Dividing both sides of the equation by d[B] gives the reverse of equation (1.3), defining the buffer capacity. Equations (1.2) and (1.3) have been defined for monoproteic acids, but are also applicable as an initial approximation to di-acids, such as tartaric and malic acids. 

The buffer capacity is the number of moles of a monoprotic strong acid or base that causes l.O L to change pH 1.0. 

Treatment of buffer efficiency in general is not limited to examination of various monoprotic and polyprotic acids, but rather to the behavior of mixtures of acids. Further, from plots of buffer index vs. pH, it is easy to see that strong acids and bases are reasonable buffers for the extreme (low and high) Ph ranges. This leads to the definition of a buffer as a solution that has neutralization capacity, rather the more limited but commonly used definition as a mixture of a weak acid and its conjugate base (See Figure 8.5). 

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