Thermodynamic Favorability and Gibbs Free Energy

Gibbs Free Energy (ΔG°)

Indicates spontaneity; negative value means favorable.

Exothermic Reaction (ΔH° < 0)

Releases heat, generally thermodynamically favored.

Endothermic Reaction (ΔH° > 0)

Absorbs heat, less likely to be favorable.

Change in Enthalpy (ΔH°)

Heat content change during a reaction.

Change in Entropy (ΔS°)

Measure of disorder in a system.

Positive Entropy Change (ΔS° > 0)

Increases disorder, favors spontaneity.

Negative Entropy Change (ΔS° < 0)

Decreases disorder, less favorable for spontaneity.

Thermodynamic Favorability Conditions

Criteria for reactions to be spontaneous.

ΔG° Calculation Formula

ΔG° = ΔH° - TΔS°.

Favorable Conditions (ΔH° < 0, ΔS° > 0)

Always favored at all temperatures.

Favorable Conditions (ΔH° < 0, ΔS° < 0)

Favored at low temperatures only.

Favorable Conditions (ΔH° > 0, ΔS° > 0)

Favored at high temperatures only.

Unfavorable Conditions (ΔH° > 0, ΔS° < 0)

Never favored at any temperature.

Coupled Reactions

Positive ΔG° can proceed with large negative ΔG°.

Kinetic Factors

Speed of reaction not guaranteed by thermodynamic favorability.

Temperature in Kelvin (T)

Used in Gibbs free energy calculations.

Microstates

Different configurations contributing to system disorder.

Reaction Spontaneity

Determined by Gibbs free energy change.

Activation Energy

Energy barrier that affects reaction speed.

Thermodynamic Favorability vs. Kinetics

Favorable reactions can be slow due to kinetics.