Study the following table: \begin{array}{c|c|c} \hline \begin{array}{c}\text { Buffer } \\ \text { Solution…
Study the following table:
\begin{array}{c|c|c}
\hline \begin{array}{c}\text { Buffer } \\
\text { Solution }\end{array} & \begin{array}{c}\text { Volume (in } \mathrm{mL} \text { ) of } \\
\text { 0.M Weak acid }\end{array} & \begin{array}{c}\text { Volume (in } \mathrm{mL} \text { ) of } \\
0.1 \mathrm{M} \text { sodium salt of } \\
\text { weak acid }\end{array} \\
\hline I. & 4.0 & 4.0 \\
II. & 4.0 & 40.0 \\
III. & 40.0 & 4.0 \\
IV. & 0.1 & 10.0 \\
\hline
\end{array}
Which of the two sets of butter solutions have least $\mathrm{pH}$ ?
I and II
I and III
II and III
II and IV
Solution
For a buffer solution, $\mathrm{pH}$ is given by Henderson, equation,
$
\mathrm{pH}=\mathrm{pKa}+\log \frac{[\text { salt }]}{[\text { acid }]}
$
Hence, $\mathrm{pH}$ is least when concentration of acid is higher than that of salt