Calculate the $pH$ of a buffer solution containing $0.35 \ M$ weak acid and $0.70 \ M$ of its salt with a strong base if $pK_{a}$ is $4.56$.

Which of the following pairs constitutes a buffer?

The dissociation constant of acetic acid is $x \times 10^{-5}$. When $25 \ mL$ of $0.2 \ M \ CH_3COONa$ solution is mixed with $25 \ mL$ of $0.02 \ M \ CH_3COOH$ solution,the $pH$ of the resultant solution is found to be equal to $5$. The value of $x$ is $..........$.

How many moles of sodium acetate should be added to $1 \ L$ of a $0.1 \ M$ solution of $CH_3COOH$ to give a solution of $pH = 5.5$? (Given: $pK_a$ of $CH_3COOH = 4.5$)

Assertion : In a titration of weak acid and $NaOH$,the $pH$ at half equivalence point is $pK_a$.
Reason : At half equivalence point,it forms an acidic buffer and the buffer capacity is maximum where $[acid] = [salt]$.

$20$ mL of a solution of acetic acid required $28.4$ mL of $0.1$ $M$ NaOH for its neutralization. $A$ solution $(X)$ was prepared by mixing $20$ mL of the above acetic acid and $14.2$ mL of $0.1$ $M$ NaOH solution. What is the pH of the solution $(X)$? ($pK_a$ value of acetic acid is $4.75$).