Calculate the volume of bcc unit cell if radius of an atom present in it is $1.86 \times 10^{-3} \mathrm{~cm}$.

Calculate the cryoscopic constant of solvent if depression in freezing point of 0.4 m solution of nonvolatile solute is 1.8 K .

Calculate the standard enthalpy change for synthesis of ammonia gas from following data.

i. $\quad 2 \mathrm{H}_{2(\mathrm{~g})}+\mathrm{N}_{2(\mathrm{~g})} \longrightarrow \mathrm{N}_2 \mathrm{H}_{4(\mathrm{~g})} ; \Delta_{\mathrm{r}} \mathrm{H}_1^0=95.4 \mathrm{~kJ}$

ii. $\quad \mathrm{N}_2 \mathrm{H}_{4(\mathrm{~g})}+\mathrm{H}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{NH}_{3(\mathrm{~g})}$;$$ \Delta_{\mathrm{t}} \mathrm{H}_2^0=-187.6 \mathrm{~kJ} $$

Which of the following is structural formula of mesityl oxide?