Use Hess's law and the following equations to calculate ΔH for the reaction N2(g) + 2O2(g) N2O4(g). (Show your work.) 2NO2(g) N2O4(g) ΔH = –57.0 kJ/mol
N2(g) + O2(g) 2NO(g) ΔH = 180.6 kJ/mol
2NO2(g) 2NO(g) + O2(g) ΔH = 114.4 kJ/mol

Suppose a pair of chemical compounds a and b can react in two different ways: a + b -> c reaction 1 gives product c. a + b -> d reaction 2 gives product d. the following facts are known about the two reactions: . reaction 1 is endothermic and reaction 2 is exothermic. if a reaction vessel is charged (filled) with a and b , then at first d is produced faster than c. use these facts to sketch a qualitative reaction energy diagram for both reactions. note: because these sketches are only qualitative, the energies don? t have to be exact. they only have to have the right relationship to each other. for example, if one energy is less than another, that fact should be clear in your sketch.