As an AI language model, I am unable to perform quantum chemical calculations directly. However, I can guide you through the process of calculating the standard enthalpy change for the given reaction using experimental values.To calculate the standard enthalpy change H for the reaction, we can use the following equation:H = nHf products - mHf reactants where Hf is the standard enthalpy of formation of each substance, n and m are the stoichiometric coefficients of the products and reactants, respectively.For the given reaction: 2H2O l + 2O2 g 4H2O l The standard enthalpies of formation Hf at 25C are as follows:- H2O l : -285.8 kJ/mol- O2 g : 0 kJ/mol since it is an element in its standard state Now, we can plug these values into the equation:H = [4 -285.8 kJ/mol ] - [2 -285.8 kJ/mol + 2 0 kJ/mol]H = -1143.2 kJ - -571.6 kJ H = -571.6 kJSo, the standard enthalpy change for the reaction is -571.6 kJ.To compare this value with the one obtained using quantum chemical methods, you would need to perform quantum chemical calculations using appropriate software and compare the results. Keep in mind that there might be some discrepancies between the experimental and theoretical values due to various factors, such as the level of theory used in the calculations and the accuracy of the experimental data.