Which statement is true for most chemical reactions?
a. an energy change occurs during the breaking and forming of bonds.
b. the internal energy of the system increases during a reaction.
c. energy is released during the formation of reactants.
d. the enthalpy of the products is higher than the enthalpy of the reactants.

The statement that is true for most chemical reactions is that A. An energy change occurs during the breaking and forming of chemical bonds. As the reactants react ultimately producing products the atoms of the respective elements within the compounds if present will break and reform ultimately to produce the products, during this change energy transformation from chemical bond formation and breakage occurs, and allows one to determine whether or not a reaction releases energy or needs a substantial amount of energy based on the energy content of the reactants and products.