1. The Henderson-Hasselbach formula is commonly used to approximate the pH value of a buffersolution.
[H,AⓇ)
pH = pK, - log
[1,-148-1)
Where the constant 8 is the charge of the acid H,A.
(i) Derive the Henderson-Hasselbach equation.
We have defined the pH value of an optimum acid buffer condition which is equal to the pK, of
the acid. Some textbooks and teacher state that to obtain this optimum acid buffer, one can use one
to one ratio between the acid and the salt that contain the conjugate anion of that acid.
(ii) Justify whether the statement regarding the one to one ratio of acid and conjugate base is true
for all case.
(iii) Show that the actual ratio between the concentration of acid and the concentration of the
conjugate ion in the optimum acid buffer condition is,
[H, AⓇ] 2K,
+1
[H.-148-1] [H.,-, A8-1]
(iv) Hence, or otherwise, show that for a very dilute system Henderson-Hasselbach equation may
not work well to approximate the pH value of the buffer solution.