What is the oxidation number of underlined species in $\mathrm{PF}_6^{-}$and $\mathrm{V}_2 \mathrm{O}_7^{-4}$ ions respectively?

Calculate the molality of solution of non volatile solute having depression in freezing point 0.93 K and cryoscopic constant of solvent $1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$.

Which of the following salt solutions turns red litmus blue?

Which from following compounds is obtained when acyl chloride is hydrolysed with water?