All the given solutions have the same concentration. Mixing equal volumes of which of the following will produce a buffer solution?
$A = NH_4Cl$; $B = CH_3COONa$; $C = NH_4OH$; $D = CH_3COOH$

$A$ buffer solution can be prepared from a mixture of

One litre buffer solution was prepared by adding $0.10 \ mol$ each of $NH_3$ and $NH_4Cl$ in deionised water. The change in $pH$ on addition of $0.05 \ mol$ of $HCl$ to the above solution is $............ \times 10^{-2}$ ($Nearest$ $integer$) ($Given$: $pK_b$ of $NH_3 = 4.745$ and $\log_{10} 3 = 0.477$)

The ratio of volumes of $CH_3COOH$ $0.1 \ N$ to $CH_3COONa$ $0.1 \ N$ required to prepare a buffer solution of $pH$ $5.74$ is (Given, $pK_a$ of $CH_3COOH$ is $4.74$)

In which of the following combinations is buffer action expected?
$1$. $NH_3 + NH_4Cl$
$2$. $HCl + NaCl$
$3$. $NH_3 + HCl$ in $2 : 1$ mole ratio
Select the correct answer using the code given below.

The $pH$ of the solution containing $50 \ mL$ each of $0.10 \ M$ sodium acetate and $0.01 \ M$ acetic acid is $.......$
[Given $pK_{a}$ of $CH_{3}COOH = 4.57$] (in $.57$)