When $1.0 \ mL$ of dilute $HCl$ acid is added to $100 \ mL$ of a buffer solution with $pH = 4.0$,what will be the resulting $pH$ of the solution?

In which of the following does a buffer solution play an important role?

The $pH$ of a sodium acetate buffer solution is given by the Henderson-Hasselbalch equation: $pH = pK_a + \log \frac{[Salt]}{[Acid]}$. For acetic acid,if $[Salt] = [Acid] = 0.1 \ M$,then the $pH$ of the solution is: $[K_a = 1.8 \times 10^{-5}]$

What would be the $pH$ of a solution obtained by mixing $5 \ g$ of acetic acid and $7.5 \ g$ of sodium acetate and making the volume equal to $500 \ mL$? $(K_a = 1.75 \times 10^{-5}, pK_a = 4.76)$

What is the ratio of $pH$ for a solution containing $1 \ mol$ $CH_3COONa$ + $0.5 \ mol$ $HCl$ per liter and another solution containing $1 \ mol$ $CH_3COONa$ + $1 \ mol$ $CH_3COOH$ per liter?

Derive the equation for the calculation of $pH$ of an acidic buffer solution.