The standard enthalpy of formation of a compound is the change in enthalpy when one mole of the compound is formed from its elements in their standard states at 25C and 1 atm pressure. For water H2O , the reaction can be written as:H2 g + 1/2 O2 g H2O l The standard enthalpy of formation of water can be calculated using Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step in the reaction.In this case, we are given the heat of formation of hydrogen gas H2 as +68.32 kJ/mol and the heat of formation of oxygen gas O2 as zero. Since the heat of formation of oxygen gas is zero, it does not contribute to the enthalpy change for the formation of water.The standard enthalpy of formation of water Hf can be calculated as follows:Hf H2O = Hf H2 + 1/2 Hf O2 - Hf H2O Since Hf O2 = 0, the equation simplifies to:Hf H2O = Hf H2 - Hf H2O However, the given information is not sufficient to directly calculate the standard enthalpy of formation of water. The heat of formation of hydrogen gas is not relevant to the formation of water from its elements, as hydrogen gas is a reactant, not a product, in the formation of water.Typically, the standard enthalpy of formation of water H2O is found in reference tables or literature. The commonly accepted value for the standard enthalpy of formation of liquid water at 25C and 1 atm pressure is approximately -285.8 kJ/mol.