Bond Enthalpy
Subject:
Chemistry [1]
Tags:
? John Erickson, 2005 WS16-2BondEnergy example H2 (g) + F2 (g) ? 2HF ?Hrxn = [energy used for breaking bonds] ? [energy formed in making bonds] [436 kJ/mol + 155 kJ/mol] ? [2(567 kJ/mol)] = ? 543 kJ/mol Bond energy is defined as the amount of energy required to break a bond. These values are positive, indicating that bond breaking is endothermic. Bond energies are reported in kilojoules per mole (kJ/mol). The energy for breaking a hydrogen-hydrogen bond is 436 kJ/mol so when a hydrogen-hydrogen bond is formed the process releases 436 kJ/mol. In a chemical reaction several bonds are broken and formed. For example in the reaction below a hydrogen-hydrogen bond is broken and a fluorine-fluorine bond is broken.