Question

If a student halves the concentration of acid as well as salt then what will happen with pH of a buffer solution?

• A. Nothing
• B. $pH$ goes up because there is less total acid in the solution
• C. $pH$ goes down because there is less conjugate base to mask the presence of the acid
• D. It depends upon the original concentration of acid and salt
• E. It is impossible to predict

Answer 1

The correct option is A Nothing

Since $pH=pKa+log\frac{\left[Salt\right]}{\left[Acid\right]}$

if ${\left[Salt\right]}^1=\left[Salt\right]/2$

${\left[Acid\right]}^1=\left[Acid\right]/2$

then also ${pH}^1=pKa+log\frac{\left[Salt\right]/2}{\left[Acid\right]/2}=pH$

Thus, the pH of the buffer solution remains same.