Download
1 / 25
250 likes | 333 Views
This comprehensive guide explores Raoult’s Law, ideal solutions, nonideal solutions, Gibbs-Duhem Equation, and more in liquid-liquid chemistry. Learn about molecular interactions, vapor pressures, ideal vs. nonideal behavior, and solution properties. Discover how to apply Dalton’s Law, interpret deviations from Raoult’s Law, and understand the significance of partial molar volumes. Dive into the Gibbs-Duhem Equation, activities in nonideal solutions, and critical behavior in liquid-liquid systems. Explore topics like Henry’s Law, distillation, fractional distillation, and azeotropes. Enhance your understanding of solution chemistry with practical insights and key concepts in this informative resource.
E N D
Chem 300 - Ch 24/#1 Today’s To Do List • Raoult’s Law & The Ideal Solution • Nonideal Solutions • Why do Liquid-Liquid solutions do this?? • Gibbs tells all • Partial Molar Quantities • Gibbs-Duhem Equation
Liquid-Liquid Solutions • Both solution components are liquids • Miscible in all proportions • Composition in MF (xi) of liq. mixture • Both have vapor pressures • Dalton’s Law holds: • Ptotal = P1 + P2 • P1 & P2 are partial pressures • Pi = Yi Ptotal Yi = MF of i in vapor
Solution Properties • Vsoln = V1 + V2 ?? Maybe…not • DHmixing = +, - , 0 ?? • Properties proportional to concentration (xi)…not always.
Compare with gas mixtures • Gas: molecules far apart • Liquid: molecules close together • Gas: Attractive/repulsive forces largely ignored • Liquid: Attr/repuls forces significant • Gas: ideal gas model • Liquid: ideal solution model
Raoult’s Law • P*i vapor pressure of pure i. • Pi partial pressure of i in solution of mol fract. Xi. • Raoult’s law: • Pi = P*i Xii = 1 or 2
Ideal Soln: Ptotal vs Xbenz Pi = P*i Xi
Pos. Devia. as fcn of Alcohol chain length (alc/H2O mixt.) 1-prop methanol
Dalton’s Law & Ideal Solns • Dalton: Ptotal = P1 + P2 • Apply Raoult’s Law: • Ptotal = P*1 X1 + P*2 X2 = P*1 X1 + P*2 (1 – X1 ) = P*2 + (P*2 - P*1) X1
NonIdeal Solutions • For Nonideal gases: • Introduced fugacity (f) • For Nonideal solutions: • Introduce activity (a) • Generalized Raoult’s Law: • Pi = P*i ai (a = gX)
The Model • Ideal Solution: • Strong Intermolecular Attractive forces • But all forces Equal: A-AB-BA-B • NonIdeal Solution: • Attractive forces NOT equal: • A-A, B-B > A-B Positive Devia from RL • A-A, B-B < A-B Negative Devia from RL
Volume Nonadditivity: Partial Molar Volumes • Mixing of Ideal Solutions: • Vtotal = n1 Vm(1) + n2 Vm(2) • Nonideal Solutions: • Define a Partial Molar Volume: • Vj = (Vtotal/nj)P,T,n’ • Vtotal = n1 V1 + n2 V2
Partial Molar Volumes as function of Mol fraction Note opposite effects
Gibbs-Duhem Equation • Gtotal = n1m1 + n2 m2 • mj = (G/ nj)P,T,n’ • dG = m1 dn1 + n1 dm1 + m2 dn2 + n2 dm2 • dG = -SdT + VdP + m1 dn1 + m2 dn2 • At const T, P dG = m1 dn1 + m2 dn2 nnn • n1 dm1 + n2 dm2 = 0Gibbs-Duhem Eq.
So… • n1dm1 + n2 dm2 = 0Gibbs-Duhem Eq. • Ties together the behavior of the components in a Solution.
Next Time More Applications of G-D Eq. Critical behavior in L-L solutions Activity Henry’s Law
