$50 \, mL$ of $0.2 \, M$ ammonia solution is treated with $25 \, mL$ of $0.2 \, M$ $HCl$. If $pK_b$ of ammonia solution is $4.75$,the $pH$ of the mixture will be

In which of the following combinations is buffer action expected?
$(a)$ $NH_4OH + NH_4Cl$
$(b)$ $HCl + NaCl$
$(c)$ $NH_4OH + HCl$ in $2:1$ mole ratio
Select the correct answer using the code given below.

Which of the following solutions can act as a buffer?

$A$ buffer solution with $pH = 9$ is prepared by mixing $NH_4Cl$ and $NH_4OH$. Calculate the number of moles of $NH_4Cl$ dissolved in $1.0 \, L$ of $1.0 \, M \, NH_4OH$ solution. (Given: $K_b(NH_4OH) = 1.8 \times 10^{-5}$)

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 $.57$)

$A$ buffer solution is prepared with a concentration of $0.30 \ M \ NH_3$ and $0.20 \ M \ NH_4^+$. If the equilibrium constant for $NH_3$ is $K_b = 1.8 \times 10^{-5}$,what will be the $pH$ of this solution?