Aim 66

ΔG

Change in free energy of a reaction.

Gibbs Free Energy Equation

ΔG = ΔH - TΔS determines spontaneity.

ΔH

Change of enthalpy during a reaction.

ΔS

Change in entropy during a reaction.

Spontaneous Reaction

Occurs when ΔG is negative.

Exothermic Reaction

Reaction with negative ΔH, releases heat.

Endothermic Reaction

Reaction with positive ΔH, absorbs heat.

Entropy Increase

Positive ΔS indicates disorder increase.

Entropy Decrease

Negative ΔS indicates disorder decrease.

Combustion Reaction

Exothermic reaction producing heat and light.

Phase Change

Transition between solid, liquid, and gas states.

High Temperature

Relative term; varies by reaction context.

Low Temperature

Relative term; varies by reaction context.

Equilibrium

State when ΔG equals zero.

Reaction Evidence

Data supporting spontaneity based on ΔH and ΔS.

ΔG at Low Temps

Negative for exothermic, negative entropy reactions.

ΔG at High Temps

Negative for endothermic, positive entropy reactions.

ΔH and -TΔS

Both factors influence spontaneity of reactions.

Spontaneity Conditions

Defined by combinations of ΔH and ΔS.

Heat Transfer

TΔS represents heat needed for entropy change.

Reaction Phases

Changes in physical states affect entropy.

Reaction Example

C5H12 + 8 O2 → 5 CO2 + 6 H2O.