Exothermic or Endothermic?

Question

Is the the decompostion of gaseous dinitrogenpentoxide to gaseous nitrogen dioxide and oxygen exothermic or endothermic? If possible explain why.

THANKS!!!!!

Answer 1

1. look up the enthalpies of formation of the two nitrogen compounds that you mention.
2. multiply the data for NO2 by 2, and subtract from it the other one (the N2O5).
3. if the result is positive, then the reaction was endothermic.

Most nitrogen oxides have a positive enthalpy of formation, and some are pretty unstable. I suspect that N2O5 is among those, so the decomposition reaction that you mention is a way of attempting to reach some sort of stability.