In a laboratory experiment, an orange-colored solid compound A decomposes on heating to give a green solid residue B, a colorless gas C, and water vapor. The dry gas C, when passed over heated magnesium, produces a white solid D. D reacts with water to give a gas E, which forms dense white

Question

In a laboratory experiment, an orange-colored solid compound A decomposes on heating to give a green solid residue B, a colorless gas C, and water vapor. The dry gas C, when passed over heated magnesium, produces a white solid D. D reacts with water to give a gas E, which forms dense white fumes on exposure to HCl. What is compound A?

Accepted Answer

Ammonium dichromate ((NH4)2Cr2O7). Ammonium dichromate (orange) decomposes on heating as: (NH4)2Cr2O7 -> Cr2O3 (green) + N2(g) + 4H2O. N2 over heated Mg gives Mg3N2 (white solid D). Mg3N2 + H2O -> Mg(OH)2 + NH3 (gas E). NH3 + HCl -> NH4Cl (dense white fumes).

Solution

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