Buffer question!

[marymochan]

the efficiency of a buffer in resisting changes in pH upon addition of base or acid is referred to as the buffer capacity. one way to define this quantity, which we shall call B, is B=dx/dpH, where x is the number of moles of base added to weak acid. Note that the HH equation may be rewritten as pH=pKa+ log (x/A₀-x)

where A₀ is the total concentration of acid.

obtain an expression for B, in terms of A₀ and the fraction of acid titrated, f, where f=x/A_0. hint: it's easiest to determine dpH/dx and take the reciprocal

this is problem 14 in ch 2 of biochemistry ed. 4

the correct answer is B=(A₀/2.303)f(1-f)

I thought the answer was just to take the pH formula and use it as the denominator and use the formula for x (derived from the formula for f) as the numerator.

TIA

Edited March 28, 2016 by marymochan