What volume of $0.2 \mathrm{M} \mathrm{CH}_3 \mathrm{COOH}$ needs to be added to 100 ml of $0.4 \mathrm{M} \mathrm{CH}_3 \mathrm{COONa}$ solution to prepare a buffer of pH equal to 4.91 ? ( $\mathrm{pK}_{\mathrm{a}}$ of $\mathrm{CH}_3 \mathrm{COOH}$ is 4.76 )

Solubility product of the sparingly soluble salt $\mathrm{AgBrO}_3$ in aqueous medium is $9.3 \times 10^{-10}$ Calculate the mass in gram of $\mathrm{AgBrO}_3$ present in 100 ml of its saturated solution. (Molar mass of $\mathrm{AgBrO}_3$ is $236 \mathrm{~g} / \mathrm{mol}$ )

The conductivity of 0.01 M solution of $\mathrm{CH}_3 \mathrm{COOH}$ at 298 K is $1.65 \times 10^{-4} \mathrm{Scm}^{-1}$ What is the $\mathrm{pK}_{\mathrm{a}}$ value of the acid if $\lambda^0\left(\mathrm{H}^{+}\right)$and $\lambda^0\left(\mathrm{CH}_3 \mathrm{COO}\right)^{-1}$ are $349.1 \mathrm{Scm}^2 \mathrm{~mol}^{-1}$ and $40.9 \mathrm{Scm}^2 \mathrm{~mol}^{-1}$ respectively?