Identify the product ' $B$ ' in the following sequence of reactions.

$$ \text { Ethanenitrile } \xrightarrow{\mathrm{SnCl}_2 . \mathrm{HCl}^{\mathrm{}}} \mathrm{~A} \xrightarrow{\mathrm{H}_3 \mathrm{O}^{+}} \mathrm{B}+\mathrm{NH}_4 \mathrm{Cl} $$

Calculate work done if 1 mole of an ideal gas expands isothermally from $2 \mathrm{dm}^3$ to $2.8 \mathrm{dm}^3$ against constant external pressure 1 atm .

Calculate the osmotic pressure of 0.2 M aqueous solution of electrolyte at 300 K . If van't Hoff factor is $1.6\left[\mathrm{R}=0.0821 \mathrm{~atm} \mathrm{dm} \mathrm{K}^{-1} \mathrm{~mol}^{-1}\right]$.

Calculate the number of unit cells in 0.79 g metal if product of density and volume of unit cell is $1.58 \times 10^{-22} \mathrm{~g}$.