Question

In order to prepare a buffer solution of pH 5.74, sodium acetate is added to acetic acid. If the concentration of acetic acid in the buffer is 1.0 M, the concentration of sodium acetate in the buffer is ______M. (Round off to the Nearest Integer).
[Given: $p{K}_a$ (acetic acid) = 4.74]

Answer 1

Answer: 10
Buffer pH = 5.74
$p{K}_a$ (acetic acid) = 4.74
By Henderson-Hasselbalch equation,
$pH=pKa+log\frac{\left[\text{sodium acetate}\right]}{\left[\text{acetic acid}\right]}$

$5.74=4.75+log\frac{\left[\text{sodium acetate}\right]}{\left[\text{acetic acid}\right]}$

$log\frac{\left[\text{sodium acetate}\right]}{\left[\text{acetic acid}\right]}=5.74-4.75=0.99\approx 1$

$\frac{\left[\text{sodium acetate}\right]}{\left[\text{acetic acid}\right]}=10$

Hence, concentration of Sodium acetate is 10 M