When a mixture of ammonium chloride and potassium dichromate was heated, a stable colurless gas (A) was evolved which did not support combustion, but magnesium continued to burn in it. The gas (A) reacted with calcium carbide in an electric furnance forming a solid (B) which was slowly hydrolysed by water forming an insoluble substance (C) and the solution of a substance (D) which turned Nessler's reagent brown. Identify substances (A) to (E) and explain all the reactions involved.

When a mixture of ammonium chloride and potassium dichromate was heate

1.	When a mixture of ammonium chloride and potassium dichromate was heated, a stable colurless gas (A) was evolved which did not support combustion, but magnesium continued to burn in it. The gas (A) reacted with calcium carbide in an electric furnance forming a solid (B) which was slowly hydrolysed by water forming an insoluble substance (C) and the solution of a substance (D) which turned Nessler's reagent brown. Identify substances (A) to (E) and explain all the reactions involved.
Answer» SOLUTION :(i) `2 NH_(4)CL + K_(2)Cr_(2)O_(7) rarr UNDERSET("Amm. dichromate")((NH_(4))_(2)Cr_(2)O_(7)) + 2 KCl` (ii) `(NH_(4))_(2)Cr_(2)O_(7) overset("Heat")(rarr) underset(("A"))(N_(2)) + Cr_(2)O_(3) + 4 H_(2)O` (iii) `3 Mg + N_(2) overset(Delta)(rarr) underset("MAGNESIUM nitride")(Mg_(3)N_(2))` (iv) `underset("Calcium carbide")(CaC_(2))+N_(2) overset("Heat")(rarr) underset("Cal. cyanamide (B)")(CaCN_(2)) + C` (v) `underset((B))(CaCN_(2))+3H_(2)O rarr underset("Cal. carbonate (C)")(CaCO_(3)) + underset("Ammonia (D)")(2NH_(3))` (vi) For reaction with Nessler's reagent, refer to Eq. (i), P-5 above.