The $pH$ of blood is

At a constant temperature,the $pK_b$ of $NH_4OH$ is $4.74$. What is the $pH$ of a basic buffer containing equimolar concentrations of $NH_4OH$ and $NH_4Cl$?

$A$ certain buffer solution contains equal concentrations of $X^{-}$ and $HX$. The $K_a$ for $HX$ is $10^{-8}$. The $pH$ of the buffer is

The $pH$ of a buffer solution decreases by $0.02$ units when $0.12 \ g$ of acetic acid is added to $250 \ mL$ of a buffer solution of acetic acid and potassium acetate at $27^{\circ} C$. The buffer capacity of the solution is

In some solutions,the concentration of $H_3O^{+}$ remains constant even when small amounts of strong acid or strong base are added to them. These solutions are known as

$pH$ of a mixture of $1 \ M \ HA$ $(pK_a = 4.2)$ and $1 \ M \ NaA$ is $4.5$. In $300 \ mL$ of buffer,the volume of $HA$ is $....... \ mL$ $[log \ 2 = 0.3]$