Consider the following equilibrium constant versus...

Consider the following equilibrium constant versus temperature data for some reaction: Predict the signs for $\Delta G^{\llcorner}, \Delta H^{\circ}$, and $\Delta S^{\circ}$ for this reaction at $25^{\circ} \mathrm{C}$. Assume $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not depend on temperature.

Consider the following equilibrium constant versus temperature data for some reaction:
Predict the signs for $\Delta G^{\llcorner}, \Delta H^{\circ}$, and $\Delta S^{\circ}$ for this reaction at $25^{\circ} \mathrm{C}$. Assume $\Delta H^{\circ}$ and $\Delta S^{\circ}$ do not depend on temperature.

Key Concepts

Enthalpy

Enthalpy (?H°) represents the heat absorbed or released in a reaction at constant pressure. The sign of ?H° can be inferred from the temperature dependence of the equilibrium constant using the van’t Hoff equation. An increase in the equilibrium constant with temperature suggests an endothermic reaction (positive ?H°), while a decrease indicates an exothermic reaction (negative ?H°).

Entropy

Entropy (?S°) reflects the change in disorder or randomness in a system accompanying a reaction. Its sign is determined by the balance between the free energy and enthalpy changes, as shown in the relationship ?G° = ?H° - T?S°. A positive ?S° indicates an increase in disorder, which can help drive a reaction even if the enthalpy change is unfavorable, whereas a negative ?S° signifies a decrease in disorder.

Gibbs Free Energy

Gibbs free energy (?G°) quantifies the maximum reversible work that can be performed by a system at constant temperature and pressure. It is directly related to the equilibrium constant of a reaction through the relation ?G° = -RT ln K, where a larger equilibrium constant corresponds to a more negative free energy change, indicating a spontaneous reaction under standard conditions.

van’t Hoff Equation

The van’t Hoff equation, expressed as d(ln K)/dT = ?H°/RT², provides a quantitative relationship between the temperature dependence of the equilibrium constant and the reaction enthalpy. It allows one to deduce the sign and approximate magnitude of ?H° by analyzing how the equilibrium constant changes with temperature, linking thermal effects directly to reaction energetics.

Transcript

Please give Ace some feedback