If the $pH$ of a mixture of $10 \, mL$ of $0.1 \, M \, NH_4OH$ and $10 \, mL$ of $1 \, M \, NH_4Cl$ solution is $8$,the $pK_b$ value of $NH_4OH$ is then closest to

When $30 \ mL$ of $0.2 \ M \ NH_4OH$ is added to $30 \ mL$ of $2 \ M \ NH_4Cl$ solution. If the $pH$ of the buffer formed is $8.2$,what is the $pK_b$ of $NH_4OH$?

How many $mL$ of $0.2 \, M \, KCN$ should be mixed with $200 \, mL$ of $0.1 \, M \, HCN$ so as to make a mixture of $pH = 3$ ($pK_a$ for $HCN = 6$)?

$A$ buffer solution can be prepared by mixing which of the following?

Aqueous solutions of $HNO_{3}$, $KOH$, $CH_{3}COOH$, and $CH_{3}COONa$ of identical concentration are provided. The pair$(s)$ of solutions which form a buffer upon mixing is (are):

Which of the following mixtures will produce a buffer solution with $pH = 9$?