Question

Solution A contains a buffer formed of 2.0 M acetic acid and 0.8 M potassium acetate. Solution B contains a buffer formed of 0.2 M acetic acid and 0.08 M potassium acetate. How do the solutions compare?

• A. The pH and buffer capacity of both solutions are the same.
• B. The pH of solution A is lower than that of solution of B, but the buffer capacity is the same.
• C. The pH of solution A is the same than that of solution of B, but solution A has a greater buffer capacity
• D. The pH of solution A is lower than that of solution of B, and solution A has a greater buffer capacity than solution B

Answer 1

The correct option is A The pH and buffer capacity of both solutions are the same.

$\begin{array}{c}\text{Buffers}\\ 2MC{H}_{3}COOH,+0.8MC{H}_{3}COO{K}^{+}\end{array}$

$\begin{array}{cc}{p}^H& =p^{ka}+\log \frac{\left[salt\right]}{\left[acid\right]}\text{Buffer capacity}=p^{ka}\\ p^H& =p^{ka}+\log \frac{0.8}{2}\\ & =p^{ka}+\log 0.4\end{array}$

$\begin{array}{cc}& 0.2M{CH}_{3}COOH+0.08{CH}_2{COOK}^{+}\text{Buffer}\\ & p^H={\left(p^{ka}\right)}_{C{H}_3\cos H}+\log \frac{\left[\text{salt}\right]}{\left[\text{acid}\right]}\end{array}$

$P^H=P^{Ka}+\log \frac{0.08}{0.2}$

$P^H=P^{K_a}+{\log }_{0.4}$

Buffer

capacity $=p^{ka}$

So, The $p^H$ and buffer capacity of both

solutions are the same.