What happens when both ΔH and ΔS are negative?

When both the enthalpy change (ΔH) and the entropy change (ΔS) for a reaction are negative, the Gibbs free energy change (ΔG) can be analyzed using the Gibbs free energy equation:

ΔG = ΔH - TΔS

In this scenario, since ΔH is negative (indicating that the reaction is exothermic) and ΔS is also negative (indicating that the disorder of the system decreases), the behavior of ΔG varies with temperature.

At lower temperatures, the term TΔS (which is negative since ΔS is negative) has a lesser impact on the ΔG value. As temperature decreases, ΔG becomes more negative, making the reaction spontaneous. Conversely, as temperature increases, the TΔS term becomes larger and subtracts more from ΔH, which can potentially lead to ΔG becoming positive, indicating non-spontaneity.

Thus, the reaction becomes spontaneous as temperature decreases. The implications of ΔH and ΔS being negative really dictate that spontaneous behavior under these conditions hinges on lower temperatures.