We will sооn see thаt the reаctiоn of moleculаr hydrogen with structures containing C=C double bonds represents an important form of catalysis. The simplest example is the reaction between ethylene and hydrogen to give ethane. The balanced equation for this reaction is shown below: Using the bond dissociation energy information provided in the equation, what is the enthalpy of this reaction as written, ΔHr, in kJ/mol?