The main buffer present in our blood is.....

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 $NH_4OH$?

In a mixture of a weak acid and its salt,the ratio of concentration of acid to salt is increased ten-fold. The $pH$ of the solution

Aqueous solutions of $HNO_3$,$KOH$,$CH_3COOH$,and $CH_3COONa$ of identical concentrations are provided.
The pair$(s)$ of solutions which form a buffer upon mixing is(are):
$A$. $HNO_3$ and $CH_3COOH$
$B$. $KOH$ and $CH_3COONa$
$C$. $HNO_3$ and $CH_3COONa$
$D$. $CH_3COOH$ and $CH_3COONa$

The Henderson-Hasselbalch equation for an acidic buffer is given by $pH - pK_a = 5$. This condition holds true when:

Which among the following pairs constitutes a buffer?