TEMAS SELECTOS DE FISICOQUMICA BIENVENIDOS!! Dr. Ren D. Peralta. Dpto. de Procesos de Polimerizacin. Correo electrnico: Tel Ext Maestra en Ciencia e Ingeniera de Materiales. PEOLES CONTENIDO DEL CURSO 8. Principios extremos y relaciones termodinmicas. 9. Equilibrio qumico en una mezcla de gases ideales. 10. Equilibrio de fases en sistemas de un componente. 11. Soluciones. Ideal and Dilute Solutions Master Thermodynamics Equations Chemical Potential Diffusion from high to low potential. Chemical potential is a Partial Molar Quantity Sum of moles of components Chemical Potential of a Binary (A & B) Mixture Chem. Potential applied to other variables: Measures of Composition s = solute ; A = solvent; V = Tot. Vol. of solution. Weight %: Mole Fraction: Molarity: Molality: Different Composition Equations for different Laws Other Partial Molar Quantities Partial Molar Volume: Partial Molar Enthalpy: Partial Molar Entropy: Calculation for Partial Molar Volumes V = f(n A, n B constant P & T constant composition Add EtOH to EtOH Add water to water Calculation for Partial Molar Volumes: 100 mL EtOH and 100 mL H 2 O (A) EtOH: d = g/mLM = 46.1 g/mol (B) Water: d = g/mLM = 18.0 g/mol Raoults Law & Ideal Solutions Vapor Pressure (VP) P i (escaping tendency g) Gas Ideality => No Intermolecular forces Solution Ideality => Uniformity in Intermolecular forces. (Binary: A-A, B-B, A-B all the same) Daltons Law Raoults Law & Ideal Solutions Thermodynamics of Mixing for an Ideal Solution TDs of Mixing for an Ideal Binary (A-B) Solution See Mathcad plot Finding Minimum of G mix curve Henrys Law (Solubility of gases in liquids) In dilution solutions, each solute is surrounded by solvent molecules (uniform environment, relatively ideal.) Positive and Negative deviations from Raoults Law Endothermic Mixing versus Exothermic Mixing Phase Diagrams The Phase Diagrams of H 2 O and CO 2 Phase Diagrams Phase Diagrams for Multi-components For 2 components: Need 3 variables ( T, P, composition ) P T Most common plots: VP vs. constant T B. pt. vs. constant P Phase Diagrams for Multi-components Liquidus Curve: Vapour Curve: Phase Diagrams for Multi-components Boiling-Point Elevation Molal boiling-point-elevation constant, K b, expresses how much T b changes with molality, m S : Decrease in freezing point ( T f ) is directly proportional to molality (K f is the molal freezing-point-depression constant): Colligative Properties Figure 13.22 Solubility ( Concn vs. T ) Derivation starting with equilibrium thermodynamics, At equilibrium (constant P & T): Freezing Point Depression ( T vs. concn ) K f = molal freezing point constant, all properties of the solvent A [ units = K kg mol -1 ] Similar equation for T b Osmosis movement of a solvent from low solute concentration to high solute concentration across a semipermeable membrane. Colligative Properties Figure 13.23 Osmosis Osmotic pressure, , is the pressure required to stop osmosis: Colligative Properties Application to Polymeric Solutions Ideal and Dilute Solutions