What does a negative enthalpy change in a reaction suggest?

A negative enthalpy change indicates that energy is being released during the reaction. This release of energy typically occurs when chemical bonds are formed that are stronger than those broken during the reaction, thus providing a net output of energy. Such reactions are termed exothermic.

In an exothermic reaction, the overall energy of the products is lower than that of the reactants, contributing to the stability of the products compared to the reactants. This is a fundamental concept in thermochemistry, where the enthalpy change gives insight into the energetic transitions that occur during chemical processes.

The other choices do not accurately describe the implications of a negative enthalpy change. For instance, if a reaction requires energy input, it would correspond to a positive enthalpy change. Similarly, a state of equilibrium does not inherently indicate the sign of the enthalpy change, and while it's true that more stable products do result from some reactions, this stability is a consequence of the energy dynamics rather than the direct result of the enthalpy change itself.