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Ammonium dichromate, (NH4)2Cr2O7, is used in fireworks (the 'volcano' demonstration). On decomposition it throws up a green powder. This green solid is:

1. Cr2O3
2. CrO2
3. Cr2O4
4. CrO3

Correct answer: Cr2O3

Solution

(NH4)2Cr2O7 decomposes to give green Cr2O3 along with N2 and H2O.

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