The potential energy in molecules is stored in

Energy, Molecules and Chemical Reactions. Energy, potential energy, is stored in the covalent bonds holding atoms together in the form of molecules. This is often called chemical energy. Except at absolute zero (the coldest temperature it is possible to reach), all molecules move.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

put the answers   and i could answer.