In a spontaneous reaction, which combination of ∆H and ∆S is possible at higher temperatures?

In a spontaneous reaction, the Gibbs free energy change (∆G) must be negative. The relationship between ∆G, enthalpy change (∆H), and entropy change (∆S) is expressed by the equation:

∆G = ∆H - T∆S

Here, T represents the temperature in Kelvin. For a reaction to be spontaneous, ∆G must be less than zero, which can be represented as:

0 > ∆H - T∆S or T∆S > ∆H.

To analyze the scenario of higher temperatures, we can consider the different combinations of ∆H and ∆S:

1. When both ∆H and ∆S are positive (+∆H and +∆S), as temperature increases, the positive T∆S term will eventually dominate the equation only if T is sufficiently large. However, depending on the magnitude of ∆H compared to T∆S, this combination may or may not lead to spontaneity.

2. When both ∆H and ∆S are negative (-∆H and -∆S), the reaction becomes less likely to be spontaneous at higher temperatures because increased temperature could make T∆S even more negative, hence making ∆G