Question

$pH$ of the solution containing equimolar amount of $C{H}_{3}COOH$
$(p{K}_a=4.74)\text{and}C{H}_{3}CO{O}^{-}$ at ${50}^{\circ }C$ is:

• A. Less than 4.74
• B. More than 4.74
• C. Equal to 4.74
• D. None of these

Answer 1

The correct option is C Equal to 4.74

$pH$ of an acidic buffer is given by
$pH=p{K}_a+log\frac{\left[salt\right]}{\left[acid\right]}$
$pH=p{K}_a+log\frac{\left[C{H}_{3}CO{O}^{-}\right]}{\left[C{H}_{3}COOH\right]}$
since $\left[C{H}_{3}CO{O}^{-}\right]=\left[C{H}_{3}COOH\right]$
$pH=p{K}_a=4.74$