Final answer:
The term likely refers to the standard enthalpy of formation, a value that indicates how much heat is released or absorbed during the formation of one mole of a compound.
Step-by-step explanation:
The agreed upon formation that is reasonably anticipated and difficult to calculate likely refers to the standard enthalpy of formation. This term describes how much heat is released or absorbed when one mole of a compound forms from its elements at standard state. Though it can often be challenging to determine experimentally, tabulated values of standard free energies of formation and enthalpies of formation allow chemists to calculate these values for a wide variety of chemical reactions, using Hess's law or other thermodynamic principles.
To calculate the enthalpy or free energy of a reaction that isn't directly measurable, one can use these standard values along with the stoichiometry of the reaction in question. For instance, in Hess's law problems, if direct measurement isn't possible, one can sum the enthalpies of formation of reactants and products to find the overall enthalpy of reaction. This process highlights the importance of flexibility and estimation when dealing with uncertainties in experimental chemistry.