Question

A physician wishes to prepare a buffer solution of pH = 3.58
that efficiently resists a change in pH yet contains only
small concentrations of the buffering agents. Which one of
the following weak acids together with its sodium salt would
be the best to use ?
(a) m-chlorobenzoic acid (pKₐ = 3.98)
(b) p-chlorocinnamic acid (pKₐ = 4.41)
(c) 2, 5-dihydroxybenzoic acid (pKₐ = 2.97)
(d) Acetoacetic acid (pKₐ = 3.58)

Answer 1

A physician wishes to prepare a buffer solution of pH = 3.58 that efficiently resists a change in pH yet contains only small concentrations of the buffering agents. Acetoacetic acid (pKₐ = 3.58) together with its sodium salt would be the best to use.

• Option (d) is correct.
• Henderson's equation is given by,
• pH = pKa + \log{10} [salt]/[acid]
• when [salt] = [acid]
• we have,
• pH = pKa
• given,
• pKa = 3.58
• Therefore, pH = 3.58
• The acid with pH = 3.58 is acetoacetic acid.