-If the change of enthalpy of this reaction when proceeding left to right is 14 kcal, which chemical equation is correct?

N2O4 <--> 2NO2 + 14 kcal
N2O4 <--> 2NO2, HR = +14 kcal
N2O4 + 14 kcal <--> 2NO2
N2O4 <--> 2NO2, HR = -14 kcal

In order for a high temperature boiler or steam engine to produce superheated water, or steam: the heat source must be greater than 100°c the water must be permitted to evaporate quickly the system must be sealed and become pressurized above atmospheric pressure the vapor pressure must be kept below 760 mm(hg)