Paragraph : Test (Q). A compound ' X ' was fused with Na metal and...

Paragraph : Test (Q). A compound ' X ' was fused with Na metal and the extract gave a white precipitate with $\mathrm{AgNO}_3$. The Lassaigne's extract gave red colouration with neutral $\mathrm{FeCl}_3$. Test $\mathbf{R}$ While compound ' Y ' when fused with Na metal and subsequent analysis on its Lassaigne's extract did not give any characteristic test. Test $\mathbf{S}$ While compound Y on fusion with fusion mixture (sodium carbonate + potassium nitrate) or $\mathrm{Na}_2 \mathrm{O}_2$, followed by extraction, followed by addition of conc. $\mathrm{HNO}_3$ and ammonium molybdate gave a yellow precipitate.Question : Compound $Y$ contain