The $pH$ of the blood buffer $CO_2-HCO_3^-$ is $7.4$. The ratio of conjugate base to acid is ....... $(K_a (H_2CO_3) = 4.5 \times 10^{-7})$

$20 \ mL$ of $0.1 \ M$ $NaOH$ is added to $50 \ mL$ of $0.1 \ M$ acetic acid solution. The $pH$ of the resulting solution is $....... \times 10^{-2}$ (Nearest integer).
Given: $pKa$ $(CH_3COOH)$ $= 4.76$,$\log 2 = 0.30$,$\log 3 = 0.48$.

In a mixture of acetic acid and sodium acetate,the ratio of the concentration of the salt to the acid is increased ten times. Then the $pH$ of the solution:

For a weak acid $(HA)$,$pK_a = 4.5$. The $pOH$ of a buffer solution of $HA$ in which $50\%$ of the acid is ionized is:

Find the $pH$ of a solution formed by mixing equal volumes of $0.1 \text{ M}$ sodium propionate and $0.1 \text{ M}$ propionic acid. (Given: The dissociation constant of propionic acid is $K_a = 1.3 \times 10^{-5}$)

Find $pH$ of the resultant solution formed by the addition of $500 \ mL$ $0.1 \ M$ $Ba(OH)_2$ and $500 \ mL$ $0.6 \ M$ $NH_4Cl$ in $1 \ L$ pure $H_2O$ at $25 \ ^oC$ (Use $\log \ 2 = 0.3$,$\log \ 3 = 0.5$,$\log \ 5 = 0.7$,$K_b(NH_3) = 10^{-5}$)