Criteria for equilibrium and spontaneity
Chemical Thermodynamics · Chemistry
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A reaction has ΔG° = +25 kJ at 298 K. Is it spontaneous? Can products still form? Step 1: ΔG° > 0 → NOT spontaneous under standard conditions. Step 2: K = e^(−ΔG°/RT) = e^(−25000/(8.314×298)) = e^(−10.1) ≈ 4×10⁻⁵. Step 3: K tiny → equilibrium lies far left, but SOME product exists. Step 4: Couple it to a ΔG < 0 reaction (like ATP hydrolysis) → driven forward. Biology runs uphill reactions by coupling them downhill.