Question

For a weak acid $p{K}_a$ is $4.8$, what will be the ratio of concentration of acid and salt in pH $5.8$ solution?

• A. $10$
• B. $3$
• C. $9$
• D. $0.1$

Answer 1

The correct option is D $0.1$

$\because pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

$5.8=4.8+\log \frac{\left[salt\right]}{\left[acid\right]}$

or $\log \frac{\left[salt\right]}{\left[acid\right]}=1.0$

$\frac{\left[salt\right]}{\left[acid\right]}=antilog1.0=10$

$\frac{\left[acid\right]}{\left[salt\right]}=\frac{1}{10}=0.1$