Which from following nitrogen bases either of purine or pyrimidine does NOT contain $-\mathrm{NH}_2$ group attached with its ring?

Which from following amino acids contains heterocyclic ring at a side chain (R) group?

Calculate the volume occupied by all particles in fcc unit cell if volume of unit cell is $1.6 \times 10^{-23} \mathrm{~cm}^3$.

Calculate the number of $\mathrm{Cl}^{-}$ions in 222 g unhydrous calcium chloride?

(At. mass $\mathrm{Ca}=40, \mathrm{Cl}=35.5$ )