By adding a strong acid to the buffer solution,the $pH$ of the buffer solution

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 dissociation constant of a weak acid is $1 \times 10^{-4}.$ In order to prepare a buffer solution with a $pH = 5,$ the $[Salt]/[Acid]$ ratio should be

Which of the following may be added to one litre of water to act as a buffer?

The $pH$ of a buffer solution obtained by mixing $50 \ mL$ of $0.1 \ M$ $NH_4OH$ and $25 \ mL$ of $2.0 \ M$ $NH_4Cl$ is ($pK_b$ of $NH_4OH$ is $4.8$).

Which buffer solution out of the following will have $pH > 7$?