To calculate the standard heat of formation of water H2O using the bond dissociation energies of H2 and O2 and the standard heat of combustion of methane CH4 , we can use the following information:1. Bond dissociation energy of H2: 436 kJ/mol2. Bond dissociation energy of O2: 498 kJ/mol3. Standard heat of combustion of methane CH4 : -890 kJ/molFirst, we need to write the balanced chemical equations for the combustion of methane and the formation of water:CH4 + 2O2 CO2 + 2H2ONow, we can use Hess's Law to calculate the standard heat of formation of water. Hess's Law states that the change in enthalpy H for a reaction is the same whether it occurs in one step or several steps. We can break down the combustion of methane into three steps:Step 1: Breaking the H2 bond requires energy H2 2H H1 = +436 kJ/mol Step 2: Breaking the O2 bond requires energy O2 2O H2 = +498 kJ/mol Step 3: Formation of water from H and O atoms releases energy 2H + O H2O H3 = ? Now, we can use Hess's Law to relate these steps to the combustion of methane:H_combustion = H1 + H2 + 2 * H3-890 kJ/mol = 436 kJ/mol + 498 kJ/mol + 2 * H3Solving for H3:H3 = -890 - 436 - 498 / 2H3 = -1824 / 2H3 = -912 kJ/molSo, the standard heat of formation of water H2O is -912 kJ/mol.