$A$ buffer solution is prepared by mixing $0.2 \ M$ sodium acetate and $0.1 \ M$ acetic acid. If $pK_{a}$ for acetic acid is $4.7$,find the $pH$.

Which of the following statements is incorrect for a buffer solution?

The dissociation constant of $HCN$ is $5 \times 10^{-10}$. The $pH$ of the solution prepared by mixing $1.5 \, mole$ of $HCN$ and $0.15 \, mole$ of $KCN$ in water and making up the total volume to $0.5 \, dm^3$ is (in $.302$)

$A$ buffer solution can be prepared from a mixture of

$A$ buffer solution of $100 \ mL$ has a $pH$ value of $4$. When $1 \ mL$ of dilute $HCl$ is added to it,what happens to the $pH$ of the buffer solution?

The buffering action of a mixture of $CH_3COOH$ and $CH_3COONa$ is maximum when the ratio of salt to acid is equal to .......?