To calculate the standard enthalpy change for the formation of ethylene oxide C2H4O , we can use the following equation:H reaction = Hf products - Hf reactants where H reaction is the standard enthalpy change for the reaction, Hf products is the sum of the standard enthalpies of formation of the products, and Hf reactants is the sum of the standard enthalpies of formation of the reactants.For the given reaction:C2H4 g + 1.5 O2 g -> C2H4O g We are given the standard enthalpy of formation of C2H4 g as 52.5 kJ/mol and that of O2 g as 0 kJ/mol. We need to find the standard enthalpy of formation of C2H4O g , which we will denote as Hf C2H4O .Using the equation above, we can write:H reaction = [Hf C2H4O ] - [Hf C2H4 + 1.5 * Hf O2 ]We are given the standard enthalpy change for the reaction H reaction as an unknown value, which we will denote as x. Therefore, we can write:x = [Hf C2H4O ] - [52.5 + 1.5 * 0]x = Hf C2H4O - 52.5Now, we need to find the value of x, which is the standard enthalpy change for the reaction. This can be found in literature or experimental data. Once we have the value of x, we can solve for Hf C2H4O :Hf C2H4O = x + 52.5