Home > Uncategorized > Thermodynamics and Kinetics Lecture 18 Notes: One Phase Equilibria

Thermodynamics and Kinetics Lecture 18 Notes: One Phase Equilibria

Overview
Today’s lecture costs 51 minutes. LOL, looks like even the glorious MIT students don’t enjoy participating in class. He has to go to lengths to get them to take a shot – just like students at every other university.

Details
Phase equilibria is different chemical equilibria, which we have been doing.

So we have two phases in equilibrium. Ice in water. Even solid-gas EQ is possible.

With T and P specified, G will tell us all. u = G/n. At EQ, G needs to be the same in all phases. The progression is from high u to low u.

Phase diagrams summarizes behavior for all Ps and Ts. What phase is present at EQ? The typical Y shaped with s on the left, gas on the bottom. At low T, solid.

The lines are coexistence curves, where two phases exist.

The lower the pressure, the higher the boiling point. The end point is the critical point. The 3 phrase equilibriujm is the critical point.

F = 3 – P
F degrees of freedom
P phases in EQ

dP/dT = dS/dV

dP/dT = dH/TdV

dH=TdS

From liquid to gas, V increases, S increases.

From solid to gas, V increase, S increase.

From solid to liquid, small V increase, S increase

du = -S dT + V dP
(dU/dT)P = -S
(dU/dP )T = V

u versus T is steepest for the gas, less so for the liquid, and the solid is the most flat. All functions are linear decreasing. Matter will be in the phase of smallest u.

The S-L EQ goes up to infinity. The L-G EQ has a critical point. Supercritical water becomes a good solvent for organics. The distinction of L and G is lost because the density changes.

Review
G=H-TS=-RT lnK=-nFE

Intermolecular Forces: ionic, h bonding, dipole dipole, VdW

1st Law: dU = dq + dw
2nd Law: dS= dq/T
3rd Law: At Ok, S=0

The five techniques: wall-standing, hooding, subjection to noise, deprivation of sleep, and deprivation of food and drink

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