Chemistry I / Gibbs Free Energy and Spontaneity
Practice question · Estimate

A reaction has ΔH=+30\Delta H = +30 kJ/mol and ΔS=+100\Delta S = +100 J/mol/K. Set the temperature in kelvin above which it becomes spontaneous.

Estimate on a scale from 0 K (0) to 600 K (600).

Hints
  1. The crossover is where the two competing terms are exactly equal.
  2. Compute 30000 / 100.
Show the answer

300 (answers within ±25 count)

Why

The crossover is T=ΔH/ΔS=30,000/100=300T = \Delta H/\Delta S = 30{,}000/100 = 300 K. Above it the TΔST\Delta S term outgrows the enthalpy penalty and the reaction becomes spontaneous.

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