Question

For preparing a buffer solution of pH 6 by mixing sodium acetate and acetic acid, the ratio of the concentration of salt and acid should be ($K_a$=${10}^{-5}$)

• A. $1:10$
• B. $10:1$
• C. $100:1$
• D. $1:100$

Answer 1

The correct option is B $10:1$

$K_a={10}^{-5};pH=6$

$pH=-\log K_a+\log \frac{\left[Salt\right]}{\left[Acid\right]};6=-\log {10}^{-5}+\log \frac{\left[Salt\right]}{\left[Acid\right]}$

$6=5\log 10+\log \frac{\left[Salt\right]}{\left[Acid\right]};6=5+\log \frac{\left[Salt\right]}{\left[Acid\right]}$

$\log \frac{\left[Salt\right]}{\left[Acid\right]}=6-5=1;\frac{\left[Salt\right]}{\left[Acid\right]}=\frac{10}{1}$