Ammonium dichromate, (NH4)2Cr2O7, is used in fireworks (the 'volcano' demonstration). On decomposition it throws up a green powder. This green solid is:
Cr2O3
CrO2
Cr2O4
CrO3
Correct answer: Cr2O3
Solution
(NH4)2Cr2O7 decomposes to give green Cr2O3 along with N2 and H2O.