$100 \ mL$ of $0.1 \ M$ $HA$ (weak acid) and $100 \ mL$ of $0.2 \ M$ $NaA$ are mixed. What is the $pH$ of the resultant solution? ($K_{a}$ of $HA$ is $10^{-5}$; $\log 2 = 0.3$)

The $pH$ of a solution containing $0.1 \ N$ $NH_4OH$ and $0.1 \ N$ $NH_4Cl$ is $9.25$. What is the $pK_b$ for $NH_4OH$?

$20 \ mL$ of $0.1 \ M$ acetic acid is mixed with $50 \ mL$ of potassium acetate. $K_a$ of acetic acid $= 1.8 \times 10^{-5}$ at $27^{\circ} C$. Calculate the concentration of potassium acetate if the $pH$ of the mixture is $4.8$. (in $M$)

An acidic buffer is obtained on mixing

Find the $pH$ when $0.2 \, mol$ of $HCl$ is added to $1 \, L$ of a solution containing $1 \, M$ $CH_3COOH$ and $1 \, M$ $CH_3COO^-$. Assume the total volume remains $1 \, L$. Given $K_a$ for $CH_3COOH = 1.8 \times 10^{-5}$.

When a buffer solution of sodium acetate and acetic acid is diluted with water,