⚡ spontaneous vs non‑spontaneous ⚡

Gibbs free energy · entropy · enthalpy — animated study deck

📌 keynotes

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spontaneous

ΔG < 0 · occurs without external intervention
✅ exergonic · may be fast or slow
🧪 example: rusting, ice melting above 0°C

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non‑spontaneous

ΔG > 0 · needs continuous energy input
⛔ endergonic · reverse is spontaneous
🧪 example: water electrolysis, photosynthesis

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ΔG = ΔH – TΔS

Gibbs free energy formula
⚖️ ΔH (enthalpy), ΔS (entropy), T (kelvin)
💡 sign of ΔG decides spontaneity

🧠 mnemonics & memory aids

✨ “GHS” — G < 0 → go! (spontaneous) · G > 0 → gotta pump energy

✨ “HITS” — High T Inverts Sign (when ΔS positive, high T makes ΔG negative)

✨ “NOSE” — Non‑spontaneous: Opposite Sign of Entropy? Actually remember: if ΔH +, ΔS + → spontaneous at high T; if ΔH +, ΔS – → never spontaneous.

💡 pro tips & tricks

🔹 ΔG° = –RT ln K : if K>1 → spontaneous (ΔG<0)

🔹 At equilibrium ΔG = 0 (system is balanced)

🔹 Spontaneous ≠ fast (kinetics vs thermodynamics)

🔹 Entropy (ΔS) : disorder increase favours spontaneity

🔹 Exothermic (ΔH negative) often spontaneous but not always

🔹 Use mnemonic “BEST” : B=by itself, E=energy negative (ΔG), S=spontaneous, T=true

📝 10 MCQs · test yourself

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