上游充通大粤 SHANGHAI JIAO TONG UNIVERSITY 9.1 Freezing point depression(1) The Gibbs free energy change from solid to liquid: partial molar AG=RTIn=RTname G molar f ∫s,pure T △G=RTIna,pwe Liquid 个 if dspue=1 Liquid and solid Tm(melting are at equilibrium temperature) At Tm,solid and liquid are at equilibrium, Solid AG=0,therefore,a.pure-1 at temperatures below Tm UJIAO TONG UMA ACineling-AIm-TASmc=L-TASg Phase diagram of a single- component system L:latent heat of fusion熔解潜热 Assume AHl and AS are independent of temperature AtTm,△melting=0=>L=Tm△Smelting 59.1 Freezing point depression (1) if 1 ln ln ln , , , ,       s pure l pure s pure l pure s l a G RT a f a RT f f G RT Tm(melting temperature) T Liquid Solid Phase diagram of a single- component system Liquid and solid are at equilibrium The Gibbs free energy change from solid to liquid : At Tm, solid and liquid are at equilibrium, ΔG = 0, therefore, Gmelting  H melting TS melting  L TS melting 1 al, pure  L: latent heat of fusion 熔解潜热 at temperatures below Tm Assume ΔH and ΔS are independent of temperature At Tm, ΔGmelting = 0 => L = Tm ΔSmelting G G partial molar molar 5