What volume (in $mL$) of $0.10 \, M$ sodium formate is required to be added to $50 \, mL$ of $0.05 \, M$ formic acid to prepare a buffer solution with $pH = 4.0$? (Given: $pK_a$ of formic acid $= 3.7$)

$A$ solution of $H_3BO_3$ and borax is known as:

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

Which of the following buffers will have a $pH$ value greater than $7$?

$A$ 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 $1.8 \times 10^{-5}$.

$A$ buffer solution can be prepared by mixing equal volumes of