Calculate the solubility of certain gas in solvent with pressure $3$ atm at $25^\circ\text{C}$ (Henry's law constant is $3.0 \times 10^{-2}\,\text{mol dm}^{-3}\,\text{atm}^{-1}$)

What is molar conductivity of $\text{CH}_3\text{COOH}$ at zero concentration if the molar conductivities of $\text{H}_2\text{SO}_4$, $\text{K}_2\text{SO}_4$ and $\text{CH}_3\text{COOK}$ at zero concentrations are respectively x, y and z $\Omega^{-1}\text{cm}^2\text{mol}^{-1}$ ?

What must be the molarity of $\text{BaCl}_2$ solution to have molar conductivity $240\,\Omega^{-1}\text{cm}^2\text{mol}^{-1}$ and conductivity $0.012\,\Omega^{-1}\text{cm}^{-1}$ at $25^\circ\text{C}$ ?

Half life of a first order reaction is $900$ second. If initial concentration of reactant is $0.08\,\text{mol dm}^{-3}$ find concentration that remains after $35$ minute ?