At $25 \, ^\circ C$,the $K_a$ for $HCN$ is $5 \times 10^{-10}$. What volume (in $mL$) of $5 \, M \, KCN$ solution must be added to $10 \, mL$ of $2 \, M \, HCN$ solution to maintain a constant $pH$ of $9$?

The dissociation constant of a weak acid is $1 \times 10^{-4}.$ In order to prepare a buffer solution with a $pH = 5,$ the $[Salt]/[Acid]$ ratio should be

$20 \ mL$ of $0.1 \ (N)$ acetic acid is mixed with $10 \ mL$ of $0.1 \ (N)$ solution of $NaOH$. The $pH$ of the resulting solution is ($pK_a$ of acetic acid is $4.74$). (in $.74$)

$50 \, mL$ of $0.1 \, M \, CH_3COOH$ is being titrated against $0.1 \, M \, NaOH$. When $25 \, mL$ of $NaOH$ has been added,the $pH$ of the solution will be $.... \times 10^{-2}$. (Nearest integer)
(Given : $pK_a(CH_3COOH) = 4.76$)
$\log 2 = 0.30$,$\log 3 = 0.48$,$\log 5 = 0.69$,$\log 7 = 0.84$,$\log 11 = 1.04$

The acidic and basic strength of buffer solutions remains constant because ...

The $pH$ of blood is maintained by a proper balance of $H_2CO_3$ and $NaHCO_3$ concentrations. What volume of $5 \, M \, NaHCO_3$ solution should be mixed with $10 \, mL$ of $2 \, M \, H_2CO_3$ to maintain a $pH$ of $7.4$ (in $, mL$)? (Given: $K_a$ for $H_2CO_3 = 7.8 \times 10^{-7}$)