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 ΔHf° (kJ/mol) S° (kJ/mol K)
Cr2O3(g) –1147 0.08115
H2O(l) –242 0.1187
N2(g) 0 0.1915
(NH4)2Cr2O7(s) –22.5 0.1137

Determine ΔSuniv° (in kJ/mol K).

a) 6.39 b) 7.66 c) 6.03 d) 84.3 e) 5.22