At lower temperatures, which combination of ∆H and ∆S indicates a spontaneous reaction?

A spontaneous reaction is determined by the Gibbs free energy change (∆G), which can be expressed as:

∆G = ∆H - T∆S

where ∆H represents the change in enthalpy, ∆S is the change in entropy, and T is the temperature in Kelvin.

For a reaction to be spontaneous, ∆G must be negative. Evaluating the combinations of ∆H and ∆S:

When ∆H is negative (exothermic), it contributes to making ∆G more negative, favoring spontaneity. Meanwhile, if ∆S is positive, this indicates an increase in disorder in the system, which also contributes to a negative ∆G when multiplied by the temperature (T).

Specifically, the combination of negative ∆H and positive ∆S results in a situation where both factors push ∆G to become negative, particularly at lower temperatures, where the impact of T∆S is less pronounced. Therefore, this combination is the most favorable for spontaneity under these conditions.

The other combinations present scenarios where either the enthalpy change or the entropy change might hinder spontaneity, such as an increase in enthalpy without a significant rise in entropy or both being