文档介绍：Chapter 7
ponent Phase Equilibrium
1
The Phase Rule
Phase: a state of matter that is uniform throughout in position and physical state. (Gibbs)
Number of phase (p):
Gas or gaseous mixture – single phase
Liquid – one, two and three phases
two tally miscible liquids – single phase
a slurry of ice and water – two phases
Solid – a crystal is a single phase
an alloy of two metals – two phases (immiscible)
- one phase (miscible)
Physical Chemistry
Chapter 7
2
The Phase Rule
(a)
(b)
The difference between (a) a single-phase solution, in which position is uniform on a microscopic scale, and (b) a dispersion, in which regions of ponent are embedded in a matrix of a ponent.
Physical Chemistry
Chapter 7
3
The Phase Rule
The difference between (a) constituent and (b) component
constituent: a chemical species (an ion or a molecule) that is present in a system
component: a chemically independent constituent of a system
number ponents (c): the minimum number of independent species necessary to define position of all the phase present in the system
Physical Chemistry
Chapter 7
4
The Phase Rule
When no reaction takes place,
The number of constituent = the number ponent
Pure water:
a ponent system
Mixture of ethanol and water:
a ponent system
water
ethanol
water
Physical Chemistry
Chapter 7
5
The Phase Rule
When a reaction takes place,
CaCO3(s) CaO(s) + CO2(g)
Phase 1
a ponent system
CaO
CO2
Phase 2
Phase 3
CaO + CO2 CaCO3
Physical Chemistry
Chapter 7
The number of constituent the number ponent
6
The Phase Rule
ponents
NH4Cl(s) NH3(g) + HCl(g)
Phase 1
a ponent system
NH4Cl
Phase 2
NH4Cl NH3 + HCl
How ponents are present in a system in which ammonium chloride undergoes thermal position?
three constituents
additional NH3 or HCl
ponent
Physical Chemistry
Chapter 7
7
The Phase Rule
Degree of freedom or Variance (f): the number of intensive variables that can be changed independently without disturbing the n