What happens when Delta S is positive and Delta H is positive?

When both Delta S (the change in entropy) and Delta H (the change in enthalpy) are positive, this scenario indicates that the entropic effects and the enthalpic changes are both contributing to the overall Gibbs free energy change (Delta G). The relationship is captured by the equation:

Delta G = Delta H - T * Delta S

For a process to be spontaneous, Delta G must be negative. When both Delta H and Delta S are positive, the behavior of Delta G depends on the temperature. At low temperatures, the T * Delta S term may not be large enough to overcome the positive Delta H term, resulting in a positive Delta G, making the process non-spontaneous.

However, as the temperature increases, the T * Delta S term becomes more significant. Eventually, there will be a temperature at which T * Delta S exceeds Delta H, resulting in Delta G becoming negative, and thus the process becomes spontaneous. Therefore, the process is not spontaneous at low temperatures but becomes spontaneous at high temperatures.