When a person breathes rapidly during fear or excitement,the concentration of $CO_2$ in the blood decreases. What happens to the $pH$ of the blood?

The pH of a solution obtained by mixing $5 \text{ mL}$ of $0.1 \text{ M } NH_4OH$ solution with $250 \text{ mL}$ of $0.1 \text{ M } NH_4Cl$ solution is . . . . . . $\times 10^{-2}$.

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

$A$ buffer solution is prepared in which the concentration of $NH_3$ is $0.30 \ M$ and the concentration of $NH_4^+$ is $0.20 \ M.$ If the equilibrium constant,$K_b$ for $NH_3$ equals $1.8 \times 10^{-5},$ what is the $pH$ of this solution? $(\log \ 2.7 = 0.43)$

$pH$ 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 $....... \ mL$ $[\log \ 2 = 0.3]$

What will be the change in $pH$ by adding $0.1 \ M$ $CH_3COONa$ to $0.1 \ M$ $CH_3COOH$ at $298 \ K$ temperature? (Given: $pK_a$ of $CH_3COOH = 4.74$)