- 3NO2 + H2O 2HNO3 + NO H = -138 kJ a. Endothermic or exothermic? _______________________ b. Heat is released or absorbed?_______________________ c. Temperature would go up or down? ________________ d. Rewrite the equation putting the heat in as a reactant or product. e. Sketch an energy diagram for the reaction in the box to the right.