Medium Practice — Set 2

Quick Recap — Entropy, Gibbs Energy & Spontaneity

• Entropy $S$ measures disorder; $\Delta S=\dfrac{q_{rev}}{T}$; $\Delta S_{universe}=\Delta S_{sys}+\Delta S_{surr}>0$ for a spontaneous change.
• Gibbs: $\Delta G=\Delta H-T\Delta S$; spontaneous if $\Delta G<0$; at equilibrium $\Delta G=0$.
• $\Delta G^\circ=-RT\ln K=-2.303RT\log K=-nFE^\circ$.
• Sign analysis: $\Delta H<0,\Delta S>0$ spontaneous at all $T$; $\Delta H>0,\Delta S<0$ never; the crossover is at $T=\Delta H/\Delta S$.