Nitrogen monoxide, a gas recently found to be involved in a wide range of biological processes, reacts with oxygen to give brown NO2 gas.
2 NO(g) + O2(g) ? 2 NO2(g) ?rH° = -114.1 kJ/mol-rxn
Is this reaction endothermic or exothermic? What is the enthalpy change if 1.25 g of NO is converted completely to NO2?