Wednesday, May 18, 2011

Heat of reaction (or) enthalpy of reaction


The Heat of Reaction or Enthalpy of Reaction may be defined as, “The amount of heat evolved or absorbed in a chemical reaction when number of moles of the reactants as represented by balanced chemical reaction have completely reacted.”
For Example:
                C (s)   +   O2 (g)         ------------>   CO2 (g)  ;                           DH   =   – 393.5 KJ.
                CH4 (g)  +   2O2 (g)   ------------>   CO2 (g)  +   2H2O (l)  ;       DH   =  –390 KJ.
                N2 (g)    +    3H2 (g)   ------------>   2NH3  (g)  ;                        DH  =  – 92.3 KJ   

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