Nitrogen dioxide standard enthalpy

In the manufacture of nitric acid by the oxidation of ammonia, the first product is nitric oxide, which is then oxidized to nitrogen dioxide. From the standard reaction enthalpies... 

Our analysis of the reaction of nitrogen dioxide molecules is not unique. The same type of path can be visualized for any chemical reaction, as Figure 6-20 shows. The reaction enthalpy for any chemical reaction can be found from the standard enthalpies of formation for all the reactants and products. Multiply each standard enthalpy of formation by the appropriate stoichiometric coefficient, add the values for the products, add the values for the reactants, and subtract the sum for reactants from the sum for products. Equation summarizes this procedure ... 

The standard enthalpy of combustion, AHc°, is the change in enthalpy per mole of a substance that is burned in a combustion reaction under standard conditions. In a combustion of an organic compound, carbon forms carbon dioxide gas and hydrogen forms liquid water any nitrogen present is released as N2, unless we specify that nitrogen oxides are formed. 

Use the information shown above to determine the standard enthalpy change for the formation of nitrogen dioxide shown in the reaction below ... 

Several important characteristics of the definition of enthalpy of formation will become clearer if we again consider the formation of nitrogen dioxide from the elements in their standard states ... 

Using the standard enthalpies of formation listed in Table 9.4, calculate the standard enthalpy change for the overall reaction that occurs when ammonia is burned in air to form nitrogen dioxide and water. This is the first step in the manufacture of nitric acid. 

Standard enthalpies of formation of many compounds have been measured experimentally. For example, consider the equation for the formation of nitrogen dioxide. 

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