Thermodynamics: physical equilibrium Flashcards Preview

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Flashcards in Thermodynamics: physical equilibrium Deck (11)
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1

Define a phase

A phase is a state of matter that is uniform throughout, in both chemical composition and in physical state

P is the number of phases in a system 

2

Define a constituent

A constituent is a chemical species (an ion or molecule) that is present in the system 

3

Define a component

A component is a chemically independent constituent of a system. C = the number of components in a system  

Note: C = 2 --> a binary mixture 

C = 3 --> a ternary mixture 

4

Describe Gibb's phase rule 

F = C - P + 2

F is the variance ie degrees of freedom, P is the number of phases and C is the number of components 

If F = 0, we cannot vary anything 

If F = 1, we can vary p or T

If F = 2, we can vary p and T independently

5

Define and describe the temperature dependence of free energy 

Sm > 0 for all substances. 

The phase with the lowest free energy at a given T is the most stable one. 

Two phases have the same free energy at a transition temperature 

6

Define and describe the pressure dependence of the free energy 

Vm > 0 for all substances 

Two phases have the same free energy at a transition pressure

7

Describe phase boundaries

At a phase boundary, the free energies of two coexisting phases are equal. 

It follows that dGm(1) = dGm(2)

8

Derive and explain the Clapeyron equation 

Note that all phase boundaries have positive slopes.

9

Derive the Clausius-Claperyron equation

10

Draw out and describe the experimental setup for measuring ΔVapHm

11

Define a critical point

A critical point ends a liquid-gas phase boundary