Question

Calculate the bond dissociation energy of the O-H bond in a water molecule (H2O) given the enthalpy change for the reaction:H2O (g) → H2 (g) + 1/2 O2 (g)ΔH = +483.6 kJ/mol(Note: the bond dissociation energy represents the energy required to break a bond into its constituent atoms.)

Answer 1

To calculate the bond dissociation energy of the O-H bond in a water molecule, we need to consider that there are two O-H bonds in a water molecule. The given enthalpy change  H  represents the energy required to break both O-H bonds and form H2 and 1/2 O2.H = +483.6 kJ/mol  for breaking two O-H bonds To find the bond dissociation energy for one O-H bond, we simply divide the enthalpy change by the number of O-H bonds in a water molecule:Bond dissociation energy  O-H  = H / number of O-H bondsBond dissociation energy  O-H  = 483.6 kJ/mol / 2Bond dissociation energy  O-H  = 241.8 kJ/molTherefore, the bond dissociation energy of the O-H bond in a water molecule is 241.8 kJ/mol.