12. There is $100.0\mathrm{g}$ samples of the following compounds: $\mathrm{NH}_3$ , $\mathrm{N}_2\mathrm{O}$ , HCN, $\mathrm{N}_2\mathrm{H}_4$ , and $\mathrm{HNO}_3$ . Which sample has the least mass percent of nitrogen? (A) $\mathrm{NH}_3$ (B) $\mathrm{N}_2\mathrm{O}$ (C)HCN (D) $\mathrm{HNO}_3$