Lecture 18

CHE 330 Thermodynamics April 12, Wednesday Instructors: Prof. Nicholas A. Kotov, kotov@umich.edu Bean Getsoian, getsoian@umich.edu Raghu Kainkaryam, raghu@umich.edu Homework etc 7.5, 7.18a, and 7.32  (Old Book)  9.5, 9.18a, and 9.32 (New Book) Review:  4/12 Wednesday from 3:30-5:00, 1301 EECS. Exam: 1013 Dow (holds 164), 1005 Dow (holds 62) and 1010 Dow (holds 69) Electrolyte Solutions Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Electroneutrality Ionic Conductivity Weak and strong electrolytes NaCl ? Na+ + Cl- CH3COOH ? CH3COO- + H+ Strong Weak CH3COOH CH3COOH CH3COO- H+ CH3COO- H+ CH3COOH Electrolyte Solutions Electrodialisys, EET Co. Reverse Osmosis Energy Requirements Colorado River Aqueduct of Southern California 15 to 26 million kWh/yr. Small- to medium-sized industrial facility 75,000 to 100,000 kWh/yr. (such as a large refinery, small steel mill, or large computer center) which uses Home unit for purification Shevchenko BN350 desalination unit,Caspian Sea Other Areas for Electrolytes Neuron functions Fuel cells Description of Electrolytes Separate chemical potentials and activity coefficients NaCl ? Na+ + Cl- CH3COOH ? CH3COO- + H+ AB ? v+Az+ + v-Bz- 0 = v+ z+ + v-z- 0 = NA z+ + NBz- G = solvent + undissociated+ cations + anions Gi(T,P,x) = Gi(T,P) + RTln{xi?i(T,P,x)} Gi(T,P,x) = Gi(T,P) + RTln{xi?i(T,P,x)} Gi(T,P,Mi) = Gi + RTln (Mi ?i ) GAB(T,P,MAB) = GAB + RTln (MAB ?AB ) GA(T,P,MA) = GA + RTln (MA ?A ) GB(T,P,MB) = GB + RTln (MB ?B ) Since the Gibbs energies of A and B cannot be measured independently, let?s consider them together Mean Ionic Activity Coefficient NDGD = NA GA + NBGB NDGD = v+GA + v-GB 0 = v+ z+ + v-z- GA(T,P,MA) = GA + RTln (MA ?A ) GB(T,P,MB) = GB + RTln (MB ?B ) ?v = (? A)v+ (? B)v- Mv = (MA)v+(MB)v-