Question: what does a negative standard enthalpy of reaction mean?
Answer: Δ = represents the change in the enthalpy; (ΔHproducts -ΔHreactants) a positive value indicates the products have greater enthalpy, or that it is an endothermic reaction (heat is required) a negative value indicates the reactants have greater enthalpy, or that it is an exothermic reaction (heat is produced)