Which one of the following pairs of solutions is not an acidic buffer?

$A$ solution contains $0.1 \ mol$ of acetic acid and $0.1 \ mol$ of sodium acetate in $500 \ mL$ of solution. If the $pH$ of the solution is $4.74$,find the ionization constant $(K_a)$ of acetic acid.

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

The Henderson-Hasselbalch equation for an acidic buffer is given by $pH - pK_a = 5$. This condition holds true when:

$A$ buffer solution can be prepared by mixing equal volumes of

Which of the following buffers will have a $pH$ value greater than $7$?