Calculate enthalpy of formation of HCl if Bond enthalpies of `H_2, Cl_2` and HCl are 434 kJ `mol^(-1)`, 242 kJ mo`l^(-1)` and 431 `kJ mol^(-1)` respectively.

Calculate the enthalpy of formation of water, given that the bond energies of H-H, O=O and O-H bond are 433 kJ mol^(-1), 492 kJ mol^(-1) , and 464 kJ mol^(-1) , respectively.

Calculate the standard enthalpy of combustion of CH_(4) , it standard enthalpies of formation of CH_(4(g)),H_(2)O_((l)), and CO_(2(g)) are -74.81kJ mol^(-1), -285.83kJ mol^(-1) and -393.51kJ mol^(-1) respectively.

Calculate the bond enthalpy of HCl. Given that the bond enthalpies of H_(2) and Cl_(2) are 430KJmol^(-1) and 242KJmol^(-1) respectively and Delta_(f)H^(0)HCl is -91KJmol^(-1) )