If this sedimentary rock layer is truly the oldest one of marine origin, what do you think that tells usabout the formation of earth's oceans?

answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.