The combustion of hydrogen-oxygen mixtures is used to produce very high temperatures (ca. 2500C ) needed for certain types of welding operations. Consider the reaction to be H2(g)+1/2O2(g)H2O(g)H=241.8kJ/mol What is the quantity of heat evolved, in kilojoules, when a 180g mixture containing equal parts of H2 and O2 by mass is burned? Based on the bond energies for the reaction below, what is the enthalpy of the reaction, in kJ ? H2(g)+N2(g)+2C(g)2HCN(g)