B Enthalpy of Reaction

Sample Problem B Calculate the enthalpy of reaction for the combustion of nitrogen monoxide gas, NO, to form nitrogen dioxide gas, 

Use the enthalpy of formation data in Appendix Table B-14. Solve by combining the known thermochemical equations. Verify the result by using the general equation for finding enthaipies of reaction from enthaipies of formation. 

0 PLAN AH can be found by adding all the AH values of the component reactions as specified in Hess s law. The desired equation has NO(g) and as reactants and N02(g) as the product. 

0 CHECK YOUR WORK The unnecessary reactants and products cancel to give the desired equation. The general relationship between the enthalpy of a reaction and the enthalpies of formation of the reactants and products is described in the following word equation. 

To find the necessary sums, the A// value for each reactant and each product must be multiplied by its respective coefficient in the desired equation. For the reaction of NO with O2, applying this equation gives the following value for A0 . 

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