The $OH^{-}$ concentration in a mixture of $5.0 \ mL$ of $0.0504 \ M \ NH_{4}Cl$ and $2 \ mL$ of $0.0210 \ M \ NH_{3}$ solution is $x \times 10^{-6} \ M$. The value of $x$ is ..... .
(Nearest integer)
$[ \text{Given } K_{w}=1 \times 10^{-14} \text{ and } K_{b}=1.8 \times 10^{-5} ]$

In order to prepare a buffer solution of $pH = 5.74$,sodium acetate is added to acetic acid. If the concentration of acetic acid in the buffer is $1.0 \ M$,the concentration of sodium acetate in the buffer is $......... \ M$. (Round off to the nearest integer).
[Given: $pKa$ (acetic acid) $= 4.74$]

In a mixture of a weak acid and its salt,the ratio of concentration of acid to salt is increased ten-fold. The $pH$ of the solution

What is the $pH$ of a buffer solution prepared by mixing $0.01 \ M$ weak acid and $0.02 \ M$ salt of weak acid with a strong base? $(pK_{a} = 4.680)$

Which of the following would produce a buffer solution when mixed in equal volumes?

The $pK_a$ of a weak acid $(HA)$ is $4.5$. The $pOH$ of an aqueous buffered solution of $HA$ in which $50\%$ of the acid is neutralized in its titration with a strong base $(BOH)$ is