Question

pH of a buffer solution decreases by $0.02$ units when $0.12g$ of acetic acid is added to $250mL$ of a buffer solution of a acetic acid and potassium acetate at ${27}^{o}C$. The buffer capacity of the solution is:

• A. $0.1$
• B. $10$
• C. $1$
• D. $0.4$

Answer 1

The correct option is D $0.4$

Given change in $pH=0.02$

To $250ml$ of Buffer solution $0.12g$ of acetic acid is added.

To $1000ml$ of Buffer solution $\frac{0.12\times 1000}{250}=0.48g$ of acetic acid is added

Now number of moles of acetic acid added $\frac{0.48}{60}=8\times {10}^{-3}moles$

We know that Buffer capacity $=\frac{Numberofmolesofacidaddedto1ltsolution}{Changein{P}^H}$

$=\frac{8\times {10}^{-3}}{0.02}=0.4$