Is it possible for a reaction to be nonspontaneous yet exo-thermic? Explain.

Key Concepts

Spontaneity of Reactions

Spontaneity refers to whether a reaction occurs naturally under given conditions without external influence. A spontaneous reaction has a negative Gibbs free energy change (ΔG < 0). However, spontaneity is not solely determined by enthalpy (heat content) but also by entropy (disorder), which can lead to nonspontaneous reactions even if they release heat.

Exothermic Reactions

Exothermic reactions are those that release heat to the surroundings, resulting in a negative change in enthalpy (ΔH < 0). While these reactions often favor spontaneity, they can still be nonspontaneous if the increase in entropy is insufficient to overcome the energy barrier, particularly at lower temperatures or under specific conditions.

Gibbs Free Energy

Gibbs free energy (G) combines enthalpy and entropy to determine the spontaneity of a reaction. The equation ΔG = ΔH - TΔS shows that a reaction can be exothermic (ΔH < 0) but still have a positive ΔG if the entropy change (ΔS) is negative or not large enough to offset the enthalpy term, resulting in a nonspontaneous process.