To calculate the standard molar enthalpy change for the reaction using quantum chemistry, we need to determine the energy of the reactants and products at the quantum level. This can be done using computational chemistry software, such as Gaussian or ORCA, which employs various quantum mechanical methods e.g., Hartree-Fock, Density Functional Theory, or post-Hartree-Fock methods to calculate the energies of molecules.For this example, let's assume we have used a quantum chemistry software to calculate the energies of the reactants and products. The energies obtained are:E H2 = -1.172 au atomic units E O2 = -2.914 auE H2O = -2.543 auNow, we need to calculate the energy change for the reaction:E = 2 * E H2O - 2 * E H2 - E O2 E = 2 * -2.543 - 2 * -1.172 - -2.914 E = -5.086 + 2.344 + 2.914E = 0.172 auTo convert the energy change from atomic units to kJ/mol, we use the conversion factor 1 au = 2625.50 kJ/mol:E = 0.172 au * 2625.50 kJ/molE = 451.19 kJ/molThe calculated standard molar enthalpy change using quantum chemistry is 451.19 kJ/mol. Comparing this value with the literature value of -572 kJ/mol, we see that there is a difference of 120.81 kJ/mol. This discrepancy could be due to the choice of the quantum mechanical method, basis set, or other factors in the computational chemistry calculations. To improve the accuracy of the calculated value, one could use more advanced quantum mechanical methods or larger basis sets, although this would require more computational resources.