9. Chemical Thermodynamics and thermochemistry( Chapter 6) classes 9.I. System, Universe Open system, Closed system, Isolated system 9.2. State and State function (a). State functions changes that only depends on the initial state and the final state, not on the path of ch es (b). Internal energy and Internal energy change (U, AU (c). Heat(Q)and Work (W)-they are NoT state functions Q=n C.(Tfinal- Tinitial), where C(Cp or Cv) is the molar heat capacity 9.3. Thermodynamics First Law: AU=Q-W ). Signs of△U,Q,andW (b). Calculation of the volume work (i.e. expansion, compression) Under constant external pressure(Pex):W=Pex. AV Under vacuum(Pex=0):W=0·△v=0 9.4. Enthalpy and Enthalpy change(H, AH) Relationship between△Hand△U:△H=AU+△ nasri 9.5. Thermal Chemical Equation AH and Q (heat) are extensive properties, and relate to moles of a reaction Exothermic(q>0): AH<0: Endothermic(q <0): AH>0 9. 6. Hess law When a reaction can be written as combination of a few other reactions. those thermodynamic state functions,(e.g.△U,△H,△S,△G, K) can be expressed as corresponding combination How to find out the combination coefficients of different sub-reactions? 9.7. Standard States(XT) For a pure solid or liquid they are standard states, concentration=1 For a gas>Standard states: Partial =1 atm For an ion in solution Standard states: [ion]=1 M If non-stand ard states, we need to convert,e.g.△Gr=△G°r+ R.In Q 9.8. Calculation of△H (a). Using the enthalpy of formation(△H°):△H=∑(△H° products)-x(△H° reactants) (b). Using the enthalpy of combustion(△H°):△H°=∑(△H。 reactants)-∑(△H。 products) (c). Using the bond energy(B.E.).△H°=∑(BE. reactants)-∑(B.E. products 9.9. Entropy and Entropy Change(s, As (a). Factors that affect entropy: State of matter, Temperature, Pressure, Molecular weight, molecular symmetry (b). Qualitatively, if gas molecules#↑→ΔS↑ 9.10. Thermodynamics Second Law:△ Sisolated=△ Ssystem+△ Surroundings>0 △ Sisolated>0÷ spontaneous;△ Sisolated=0 equilibrium, ISolated<0 non-spontal 9. 11. Gibbs free energy and change(GT, AGT)9．Chemical Thermodynamics and Thermochemistry (Chapter 6) 4 classes 9.1．System, surroundings, and universe  System + Surroundings = Universe  Open system, Closed system, Isolated system 9.2．State and State function (a)．State functions: changes that only depends on the initial state and the final state, not on the path of changes (b)．Internal energy and Internal energy change (U, ΔU) (c)．Heat (Q) and Work (W) – they are NOT state functions!!  Q = n ∙ C ∙ (Tfinal – Tinitial), where C (Cp or Cv) is the molar heat capacity 9.3．Thermodynamics First Law: ΔU = Q – W (a)．Signs of ΔU, Q, and W (b)．Calculation of the volume work (i.e. expansion, compression)  Under constant external pressure (Pex): W = Pex ∙ ΔV  Under vacuum (Pex = 0): W = 0 ∙ ΔV = 0 9.4．Enthalpy and Enthalpy change (H, ΔH)  Relationship between ΔH and ΔU: ΔH = ΔU + ΔngasRT 9.5．Thermal Chemical Equation  ΔH and Q (heat) are extensive properties, and relate to moles of a reaction.  Exothermic (q > 0): ΔH < 0; Endothermic (q < 0): ΔH > 0 9.6．Hess Law – When a reaction can be written as combination of a few other reactions, those thermodynamic state functions, (e.g. ΔU, ΔH, ΔS, ΔG, K) can be expressed as corresponding combination.  How to find out the combination coefficients of different sub-reactions? 9.7．Standard States (Xo T):  For a pure solid or liquid → they are standard states, concentration = 1  For a gas → Standard states: Ppartial = 1 atm  For an ion in solution → Standard states: [ion] = 1 M  If non-standard states, we need to convert, e.g. ΔGT =ΔGo T + R∙T∙ln Q 9.8．Calculation of ΔH (a)．Using the enthalpy of formation (ΔHf o ): ΔHo = ∑ (ΔHf o products) – ∑(ΔHf o reactants) (b)．Using the enthalpy of combustion (ΔHc o ): ΔHo = ∑ (ΔHc o reactants) – ∑(ΔHc o products) (c)．Using the bond energy (B.E.): ΔHo = ∑ (B.E. reactants) – ∑(B.E. products) 9.9．Entropy and Entropy Change (S, ΔS) (a)．Factors that affect entropy: State of matter, Temperature, Pressure, Molecular weight, molecular symmetry (b)．Qualitatively, if gas molecules # ↑ →ΔS ↑ (c)．ΔS o = ∑ (So products) – ∑(So reactants) 9.10．Thermodynamics Second Law: ΔSisolated = ΔSsystem + ΔSsurroundings > 0  ΔSisolated > 0 → spontaneous; ΔSisolated = 0 → equilibrium; ΔSisolated < 0 → non-spontaneous 9.11．Gibbs free energy and change (GT, ΔGT)