An orange coloured solid $(A)$ is soluble in water and gives a gas $(B)$ and green coloured solid $(C)$ on heating. The compound $(A)$ gives a gas $(D)$ when reacts with $N a O H$ and solution turns yellow. The gas $(D)$ turns red litmus blue. Identify the compounds $(A)$ to $(D)$ and explain the reaction.

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Solution

Ammonium dichromate is an inorganic compound with the formula $(N H_{4})_{2} C r_{2} O_{7}$ , chromium is in +6 oxidation state.It is a salt consisting of ammonium ions and dichromate ions. At room temperature and pressure, the compound exists as orange, acidic crystals soluble in water and alcohol. It is formed by the action of chromic acid on ammonium hydroxide with subsequent crystallisation.
Ammonium dichromate upon heating gives nitrogen gas and a dark green powdered chromium oxide, $(N H_{4})_{2} C r_{2} O_{7} (s) C r_{2} O_{3} (s) + N_{2} (g) + 4 H_{2} O (g)$
When a solution of $(N H_{4})_{2} C r_{2} O_{7}$ is heated with $N a O H$ gives Ammonia $(N H_{3})$ and a yellow solution of sodium dichromate ( $N a_{2} C r_{2} O_{7}$ ) . $N H_{3}$ is basic in aqueous solution, hence turns red litmus to blue,
$(N H_{4})_{2} C r_{2} O_{7} + N a O H 2 N H_{3} + N a_{2} C r_{2} O_{7} + 2 H_{2} O$
$(A) - (N H_{4})_{2} C r_{2} O_{7},$ $(B) - N_{2},$ $(C) - C r_{2} O_{3},$ $(D) - 2 N H_{3}$

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An orange coloured solid (A) is soluble in water and gives a gas (B) and green coloured solid (C) on heating. The compound (A) gives a gas (D) when reacts with NaOH and solution turns yellow. The gas (D) turns red litmus blue. Identify the compounds (A) to (D) and explain the reaction.