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Entropy & Spontaneity Predictor
AP Chemistry · Unit 9 Thermodynamics
Learning Objectives
Calculate ΔG = ΔH − TΔS
Predict spontaneity from signs of ΔH and ΔS
Determine crossover temperature (ΔG = 0)
Distinguish the four ΔH/ΔS sign combinations
Four Cases
−ΔH, +ΔS:
Always spontaneous
+ΔH, −ΔS:
Never spontaneous
−ΔH, −ΔS:
Spont. at low T
+ΔH, +ΔS:
Spont. at high T
Crossover: T = ΔH/ΔS
Tags
Gibbs free energy
entropy
spontaneity
ΔG
ΔH (kJ/mol)
-100
ΔS (J/mol·K)
150
Temperature (K)
298
ΔG
—
Spontaneous?
—
Crossover T
—
Case
—