Which buffer is present in human blood :-

In which of the following does a buffer solution play an important role?

Buffer Solution	Volume of $0.1 \ M$ Weak Acid (mL)	Volume of $0.1 \ M$ Sodium Salt (mL)
$I$	$4.0$	$4.0$
$II$	$4.0$	$40.0$
$III$	$40.0$	$4.0$
$IV$	$0.1$	$10.0$

Which of the two sets of buffer solutions have the least $pH$?

The $pH$ of a solution containing $0.1 \ N$ $NH_4OH$ and $0.1 \ N$ $NH_4Cl$ is $9.25$. What is the $pK_b$ for $NH_4OH$?

The $pH$ of a buffer solution formed by mixing $30 \text{ mL}$ of $0.1 \text{ M } NH_4OH$ and $30 \text{ mL}$ of $1 \text{ M } NH_4Cl$ solutions is $8.6$. The $pK_b$ of $NH_4OH$ is

$A$ buffer solution with $pH = 9$ is prepared by mixing $NH_4Cl$ and $NH_4OH$. Calculate the number of moles of $NH_4Cl$ dissolved in $1.0 \, L$ of $1.0 \, M \, NH_4OH$ solution. (Given: $K_b(NH_4OH) = 1.8 \times 10^{-5}$)