Question

$p{K}_a$ of $C{H}_{3}COOH$ is 4.74. Thus, the buffer range for $C{H}_{3}COOH$ and $C{H}_{3}COONa$ buffer is

• A. 3.74 to 4.74
• B. 4.74 to 5.74
• C. 3.74 to 5.74
• D. 1.0 to -1.0

Answer 1

The correct option is C 3.74 to 5.74

Buffer solution is most effective, when
$\left[A^{-}\right]=10\left[HA\right]$
or $\left[HA\right]=10\left[A^{-}\right]$
Thus, $pH=p{K}_a\pm \text{log}10=p{K}_a\pm 1=4.74\pm 1$
Hence, pH range will be $\pm 1$ of $p{K}_a$ value.
So, the buffer range for $C{H}_{3}COOHandC{H}_{3}COONa$ is 3.74 to 5.74