At a constant temperature,the $pK_b$ of $NH_4OH$ is $4.74$. What is the $pH$ of a basic buffer containing equimolar concentrations of $NH_4OH$ and $NH_4Cl$?

Assertion : In a titration of weak acid and $NaOH$,the $pH$ at half equivalence point is $pK_a$.
Reason : At half equivalence point,it forms an acidic buffer and the buffer capacity is maximum where $[acid] = [salt]$.

What is the ratio of concentration of salt to concentration of weak acid in a buffer solution to maintain its $pH$ value at $7.2$ $(pK_{a} = 6.2)$?

Find the concentration of sodium acetate when added to $0.1 \ M$ solution of acetic acid to form a buffer solution of $pH = 5.5$ (in $M$)? $(pK_{a} \text{ of } CH_{3}COOH = 4.5)$

Which of the following cannot act as a buffer solution?

The $pH$ of an aqueous solution containing $1 \ M$ benzoic acid $(pK_{a}=4.20)$ and $1 \ M$ sodium benzoate is $4.5$. The volume of benzoic acid solution in $300 \ mL$ of this buffer solution is . . . . . . $mL$.