average bond enthalpy of water is given by: 502+427/2=464.5 KJ/mol. Tell me what to call these no. 502 and 427 and where do they came from?
502 and 427 are the bond enthalpies of two OH bonds in water. In case of water, the enthalpy needed to break the two O – H bonds is different and thus bond enthalpy of the molecule is calculated as the average bond enthalpy which is given as :
(502 + 427) /2 = 464.5 KJ/mol