Components of a buffer solution are $0.1 \ M \ HCN$ and $0.2 \ M \ NaCN$. What is the $pH$ of the solution? (Given: $pK_a$ of $HCN = 9.30$)

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

$A$ sample of $100 \ mL$ of $0.10 \ M$ acid $HA$ $(K_a = 1 \times 10^{-5})$ is titrated with standard $0.2 \ M \ KOH$. How many $mL$ of $KOH$ will have to be added when the $pH$ in the titration flask will be $5.00$?

Find $pH$ of the resultant solution formed by the addition of $500 \ mL$ $0.1 \ M$ $Ba(OH)_2$ and $500 \ mL$ $0.6 \ M$ $NH_4Cl$ in $1 \ L$ pure $H_2O$ at $25 \ ^oC$ (Use $\log \ 2 = 0.3$,$\log \ 3 = 0.5$,$\log \ 5 = 0.7$,$K_b(NH_3) = 10^{-5}$)

Which of the following buffer solutions will have the highest acidic character?

$0.1 \ M$ formic acid solution is titrated against $0.1 \ M \ NaOH$ solution. What would be the difference in $pH$ between $1/5$ and $4/5$ stages of neutralization of acid?