A hypothetical reaction is observed to be non-spontaneous at low temperatures, but it becomes spontaneous when the temperature is raised significantly. Which of the following conditions correctly describes the enthalpy change ( H ) and entropy change ( S ) for this reaction?

Step-by-step solution

The spontaneity of a reaction is determined by the Gibbs free energy equation: G = H - T S For a reaction to be spontaneous, G must be negative ( G At low temperatures, the magnitude of the T S term is small, so the sign of G is largely determined by H . Since the reaction is non-spontaneous at low temperatures, G > 0 , which implies H > 0 . At high temperatures, the magnitude of the T S term becomes large and dominates the equation. For the reaction to become spontaneous ( G 0 . Therefore, the reaction has H > 0 a