How should the enthalpy of an intermediate step be manipulated when used to produce an overall chemical equation?

Heat is not a State function hence it depends upon intermediate steps. We use Hess's law to calculate the enthalpy of a chemical reaction. Multiply the enthalpy by 1 if the chemical equation is reversed. Multiply the enthalpy by –1 if the chemical equation is reversed. Add 2 to the enthalpy if the coefficients must be doubled. Add 2 to the enthalpy if the coefficients must be cut in half.

your answer would be a. 12.5 kg

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.