If $50 \ mL$ of $0.2 \ M \ KOH$ is added to $40 \ mL$ of $0.5 \ M \ HCOOH,$ the $pH$ of the resulting solution is $(K_a = 1.8 \times 10^{-4})$

An example of a neutral buffer is:

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

Given below are two statements:
Statement $I$: $A$ buffer solution is the mixture of a salt and an acid or a base mixed in any particular quantities.
Statement $II$: Blood is a naturally occurring buffer solution whose $pH$ is maintained by $H_2CO_3 / HCO_3^{-}$ concentrations.
In the light of the above statements,choose the correct answer from the options given below.

$20 \, mL$ of $0.2 \, M \, HCN$ is mixed with $10 \, mL$ of $0.2 \, M \, NaOH$. Calculate the $pH$ of the resulting mixture. The $pKa$ value of $HCN$ is $5$.

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 $4.74$)