When ignited, solid ammonium dichromate decomposes in a fiery display. This is the reaction for a "volcano" demonstration. The decomposition produces nitrogen gas, water vapor, and chromium(III) oxide. The temperature is constant at 25°C.

Substance H0f (kJ/mol) S0 (kJ/mol . K)

a. Cr2O3 (g) -1140 0.0812
b. H2O (I) -242 0.1187
c. N2 (g) 0 0.1915
d. (NH4)2 Cr2O7 - 22.5 0.1137