A physician wishes to prepare a buffer solution at `pH` = 3.58 that efficiently resist changes in `pH` yet contains only small concentration of the buffering agents. Which one of the following weak acid together with its sodium salt would be best to use ?

Options

A. m-chlorobenzoic acid `(pK_(a)=3.98)`
B. p-chlorocinnamic acid `(pK_(a)=4.41)`
C. 2,5-dihydroxy benzoic acid `(pK_(a)=2.97)`
D. Acetoacetic acid `(pK_(a)=3.58)`

Answer

D

Explanation

By the use of Henderson's equation
`pH=pK_(a)+log_(10).(["salt"])/(["acid"])`
When, [salt] = [acid]
`therefore pH =pK_(a)`
`because pK_(a)=3.58`, thus at this state
`pH=3.58`
So, acetoacetic acid `(pK_(a)=3.58)` is best to use.