Calculate the $pH$ of a $2 \, L$ solution containing $0.1 \, M \, CH_3COOH$ and $0.1 \, M \, (CH_3COO)_2Ba$. Given $K_a (CH_3COOH) = 1.8 \times 10^{-5}$.

Which of the following solutions does not act as a buffer?

Addition of sodium hydroxide solution to a weak acid $(HA)$ results in a buffer of $pH \ 6$. If ionisation constant of $HA$ is $10^{-5}$,the ratio of salt to acid concentration in the buffer solution will be

$50 \, mL$ of $0.1 \, M \, CH_3COOH$ is being titrated against $0.1 \, M \, NaOH$. When $25 \, mL$ of $NaOH$ has been added,the $pH$ of the solution will be $.... \times 10^{-2}$. (Nearest integer)
(Given : $pK_a(CH_3COOH) = 4.76$)
$\log 2 = 0.30$,$\log 3 = 0.48$,$\log 5 = 0.69$,$\log 7 = 0.84$,$\log 11 = 1.04$

$A$ buffer solution can be prepared from a mixture of

$A$ $0.15 \text{ mol}$ of pyridinium chloride is added to $500 \text{ cm}^3$ of $0.2 \text{ M}$ pyridine solution. Assuming no change in volume upon mixing, what is the $pH$ of the resulting solution? (Given: $pK_b$ of pyridine $= 8.75$)