华东理工大学：《物理化学》课程教学课件（讲稿，英文版）09 Chapter 9 Chemical equilibrium.pdf_大学文库

版权所有：华东理工大学物理化学教研室 2 Spontaneous chemical reactions 9.1 The Gibbs energy minimum The response of equilibria to the conditions 9.2 How equilibria respond to pressure 9.3 The response of equilibria to temperature Applications to selected systems 9.4 The extraction of metals from their oxides 9.5 Acids and bases 9.6 Biological activity:the thermodynamics of ATP 9. Chemical equilibrium

版权所有：华东理工大学物理化学教研室 3 1) The reaction Gibbs energy ⇔ BA 9.1 The Gibbs energy minimum For the simplest possible chemical equilibrium Suppose an infinitesimal amount dξ of A turns into B: The change in the amount of A present is dnA = -dξ The change in the amount of B present is dnB = + dξ . The quantity ξ is called the extent of reaction; The dimensions is amount of substance, (moles)

版权所有：华东理工大学物理化学教研室 4 1) The reaction Gibbs energy The reaction Gibbs energy, ΔrG, is defined as the slope of the graph of the Gibbs energy plotted against the extent of reaction, ξ p,T ξ G G ⎟⎠⎞ ⎜⎝⎛ ∂∂ r =Δ At constant T、p, the change in Gibbs energy is G = μ n + μ ddd nBBAA = − A + Bdd ξμξμ = − AB )d( ξμμ r μμ AB ξ G G p,T ⎟ −= ⎠⎞ ⎜⎝⎛ ∂∂ =Δ 9.1 The Gibbs energy minimum

版权所有：华东理工大学物理化学教研室 5 1) The reaction Gibbs energy As the reaction advances the slope of the Gibbs energy changes. Equilibrium corresponds to zero slope, at the foot of the valley. when μA> μB, , ΔrG0 the reaction B →A is spontaneous; ΔrG = − μμ AB when ΔrG=0: The slop is zero and the reaction is spontaneous in neither direction. The composition of the reaction mixture at equilibrium 9.1 The Gibbs energy minimum

版权所有：华东理工大学物理化学教研室 6 2) Exergonic and endergonic reactions 9.1 The Gibbs energy minimum The spontaneity of a reaction at constant temperature and pressure is expressed by the reaction Gibbs energy: If ΔrG 0, the reverse reaction is spontaneous; it is called endergonic (work-consuming) If ΔrG = 0, the reaction is at equilibrium; it is spontaneous in neither direction, and neither exergonic nor endergonic

版权所有：华东理工大学物理化学教研室 7 3) Perfect gas equilibria When A and B are perfect gases: If denote the ratio of partial pressures by Q Δ G = − μμ ABr 9.1 The Gibbs energy minimum ( μB += pRT B ()ln μ A +− pRT A )ln o o A B r ln p p +Δ= RTGo r r +Δ=Δ lnQRTGG o

版权所有：华东理工大学物理化学教研室 8 3) Perfect gas equilibria At equilibrium ΔrG = 0. When the ratio of partial pressures at equilibrium is denoted K 9.1 The Gibbs energy minimum Δr −= ln KRTGo 0 Δr += ln KRTGo A equilibrium B ⎥⎦⎤ ⎢⎣⎡ = pp K

版权所有：华东理工大学物理化学教研室 9 3) Perfect gas equilibria 9.1 The Gibbs energy minimum When > 0, K 1 : at equilibrium the partial pressure of B exceeds that of A, the product B is favoured in the equilibrium. o ΔrG

版权所有：华东理工大学物理化学教研室 10 4) The general case of a reaction For the reaction dξμν J JJ ⎟⎠⎞ ⎜⎝⎛ = ∑ a A + b B → c C + d D When the reaction advances by dξ, the amounts of reactants and products change as follows: an ξ bn ξ cn ξ dn dddddddd ξ A = − B = − C = + D = + In general , the change in the Gibbs energy at constant temperature and pressure is n dd ξν = JJ G (d cμ dμ aμ bμ d) ξ = C + D − − BA 9.1 The Gibbs energy minimum