An orange solid $\left(\mathrm{X}\right)$ on heating gives a colourless gas$\left(\mathrm{Y}\right)$ and only a green residue $\left(\mathrm{Z}\right)$. Gas $\left(\mathrm{Y}\right)$ on treatment with Mg produces a white solid substance

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\left(\mathrm{X}\right) \stackrel{\mathrm{Heat}}{⟶} {\mathrm{Cr}}_2{\mathrm{O}}_3 + {\mathrm{N}}_2 + {\mathrm{H}}_2\mathrm{O}$

$\begin{array}{ccc}\text{ Amm.dichromate }& \text{ Chromic oxides }& \text{ (Colourless gass) }\\ \text{ (orange solid) }& \text{ (Green residue) }& \text{ (Y) }\end{array}$

${\mathrm{N}}_2+\mathrm{Mg}⟶{\mathrm{Mg}}_3{\mathrm{N}}_2$

     (Y)                white