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Chem 300 - Ch 24/#3 Today’s To Do List Critical behavior in L-L solutions Activity Excess Thermo Functions.

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Presentation on theme: "Chem 300 - Ch 24/#3 Today’s To Do List Critical behavior in L-L solutions Activity Excess Thermo Functions."— Presentation transcript:

1 Chem 300 - Ch 24/#3 Today’s To Do List Critical behavior in L-L solutions Activity Excess Thermo Functions

2 T-x/y Plot

3 NonIdeal Solns Azeotropes

4 Extremes in Positive Deviations from RL: 2 Liquid Phases

5 The Lever Rule: l Consider 2 phases (‘ & “) each containing 2 components (1 & 2) in equilibrium: l Let n’ tot = n’ 1 + n’ 2 etc l n’ tot /n” tot =(x” 2 – x 2 )/(x 2 – x’ 2 ) = (length)’’/(length)’

6 C 6 H 12 /Nitrobenzene T-x 2-Phase Diagram

7 H 2 O/Triethylamine T-x with Lower Critical Point

8 H 2 O/Nicotine with upper & lower Critical T

9 Activity: Measure of Soln Nonideality l dG = -SdT + VdP l 2 phases at const T and equilibrium dG T = VdP   j soln  =  j vap  j soln  =  j vap =  j o (T) +RT ln P j l If soln is ideal (RL holds): P j = P* j x j  j soln  =  j o (T) + RT ln P* j x j =  j o (T) + RT ln P* j + RT ln x j  j soln =  j o (T) +  j *(T) + RT ln x j

10 Continued For nonideal solutions: P j = P* j a j where a j =  j x j = activity of j at x j relative to RL  j soln =  j o (T) +  j *(T) + RT ln a j l Comparing equations: a j = P real /P * a j /x i =  j = P real /P * x i = P real /P ideal

11 Measure γ & Activity (a)

12 Activities relative to (a) R L & (b) H L

13 Excess Functions  G ID mix = RT(n 1 ln x 1 + n 2 ln x 2 ) l For nonideal soln mixing:  G NID mix = RT(n 1 ln a 1 + n 2 ln a 2 )  G NID mix = RT(n 1 ln x 1 + n 2 ln x 2 +n 1 ln  1 + n 2 ln  2 ) G E =  G NID mix -  G ID mix = RT(+n 1 ln  1 + n 2 ln  2 )

14 Calculated  R for CS 2 /DMM Solns @ 35.2 ºC

15 G E -x for CS 2 /DMM Solns

16 Solution with T uc < T bp that shows Azeotrope

17 Next Time Start Chapter 25: Solid-Liquid Solutions Solute?…Solvent?… Molarity?…Molality?… Colligative Properties


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