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:

What is $[H^{+}]$ in $mol/L$ of a solution that is $0.20\, M$ in $CH_3COONa$ and $0.10\, M$ in $CH_3COOH$? $K_a$ for $CH_3COOH = 1.8 \times 10^{-5}$.

What is the total number of buffers formed during the titration of $H_3PO_4$ with $NaOH$?

An example of a neutral buffer is:

Calculate the $pH$ of a buffer solution prepared by mixing $30 \ mL$ of $0.1 \ M$ $NaOH$ and $100 \ mL$ of $0.1 \ M$ $CH_3COOH$. (Given: $pK_a$ of $CH_3COOH = 4.76$)

$A$ buffer solution is prepared by mixing $10 \ mL$ of $1.0 \ M$ acetic acid and $20 \ mL$ of $0.5 \ M$ sodium acetate and then diluted to $100 \ mL$ with distilled water. The $pH$ of the buffer solution is ($pK_a$ of acetic acid is $4.76$).