$A$ solution of $0.1 \ mol$ of $CH_3NH_2$ $(K_b = 5 \times 10^{-4})$ and $0.08 \ mol$ of $HCl$ is diluted to $1 \ L$. The $pOH$ of the resulting solution is $(\log 1.25 = 0.1)$.

Which of the following is a buffer solution?

Which of the following mixtures in water acts as a basic buffer?

Assertion $(A)$: The $pH$ of a buffer solution containing equal moles of acetic acid and sodium acetate is $4.8$ ($pK_a$ of acetic acid is $4.8$).
Reason $(R)$: The ionic product of water at $25^{\circ} C$ is $10^{-14} \ mol^2 \ L^{-2}$. The correct answer is

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

$A$ buffer solution contains equal concentrations of weak acid and its salt with a strong base. Calculate the $pH$ of the buffer solution if the dissociation constant of the weak acid is $1.8 \times 10^{-5}$.