Calculate ΔS_surr at the indicated temperature for each reaction. d. ΔH°_rxn = +114 kJ; 77 K

Key Concepts

Entropy (ΔS)

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, it quantifies the amount of energy in a physical system that is not available to do work. A positive change in entropy (ΔS > 0) indicates an increase in disorder, while a negative change (ΔS < 0) suggests a decrease in disorder. Understanding entropy is crucial for predicting the spontaneity of reactions.

Enthalpy (ΔH)

Enthalpy is a thermodynamic property that reflects the total heat content of a system. It is defined as the internal energy plus the product of pressure and volume (H = U + PV). The change in enthalpy (ΔH) during a reaction indicates whether the reaction is exothermic (ΔH < 0) or endothermic (ΔH > 0). This concept is essential for calculating the surrounding entropy (ΔS surr) using the relationship between enthalpy and temperature.

Gibbs Free Energy and Surrounding Entropy

The Gibbs free energy (G) combines enthalpy and entropy to determine the spontaneity of a reaction at constant temperature and pressure. The relationship ΔG = ΔH - TΔS allows us to calculate the change in entropy of the surroundings (ΔS surr) using the enthalpy change and the temperature. A reaction is spontaneous if ΔG is negative, which is influenced by both ΔH and ΔS surr.