which of the following absorbs hear from the surroundings as it proceeds to completion?

1. CO(g)+1/2 O2 (g)=CO2 (g)
2.AL2O3(s)=2 Al(s) + 3/2 O2 (g)
3.SO3 (g) + 99.2kJ=S (s)+3/2 O2 (g)

Hrxn = -283.0 kj (endothermic)