1112 equilibrium phases med
TRANSCRIPT
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Liquid-Vapor Equilibrium
(Intermolecular Forces and Liquids and Solids)
Green/Damji: 17.1Chang: Chapter 11
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E v a p o r a t i o
n
Greatest
Order
Least
Order
11.8
C o n d e n s a t i o n
Focus onEvaporation and
Condensation
Write an equation for the
equilibrium between liquid
water and its vapor:
Is evaporation an
endothermic or exothermic
process?
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Before
Evaporation
At
Equilibrium
11.8
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The equi l ibr ium vapor pressu re is the vapor pressure
measured when a dynamic equilibrium exists between
condensation and evaporation
H2O (l ) H2O (g )
Rate of
condensation
Rate of
evaporation=
Dynamic Equilibrium
11.8
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Factors affecting the vapor pressure
• SURFACE AREA
increasing surface area only meansequilibrium is reached faster
• TEMPERATURE
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11.8
T2 > T1
What is the name of this
diagram? Why is it
important?
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Vapor Pressure Versus Temperature
Patterns? Why?
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Enthalpy o f vaporizat ion (DH vap) is the energy required to
vaporize 1 mole of a liquid at its boiling point.
Enthalpy of vapor izat ion : physic al proc ess (phase change) as
______________________: chem ical reac t ion
11.8
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The relat ionship between vapo r pressu re and temperature
can be exp ressed mathematical ly – NOT req’d by IB
ln P = -DH vap
RT + C
Clausius-Clapeyron Equation P = (equilibrium) vapor pressure
T = temperature (K)
R = gas constant (8.314 J/K•mol)
11.8
Vapor Pressure Versus Temperature
C = integration constant
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Heating Curve
Why are there plateaus on this graph?
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The boi l ing po int is the temperature at which the
(equilibrium) vapor pressure of a liquid is equal to the
external pressure.
The normal boi l ing po int is the temperature at which a liquid
boils when the external pressure is 1 atm.
11.8
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What are the three primary intermolecular forces?
List in order of increasing strength.
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The boi l ing po int and enthalpy of vapor izat ion are
influenced by intermolecular forces…
Compound Enthalpy of
vaporization
in kJ mol-1
Boiling Point
in K
Intermolecular
Forces
methane
CH4
9.0 109
methoxy
methane
CH3OCH3
27.2 248
ethanolCH
3CH
2OH
38.6 352
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State the relationship between intermolecular
forces and enthalpy of vaporization.
State the relationship between intermolecular
forces and boiling point.
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A phase diagram summarizes the conditions at which a
substance exists as a solid, liquid, or gas.
Phase Diagram of Water
11.9
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Effect of Increase in Pressure on the Melting Point
of Ice and the Boiling Point of Water
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Textwork 17.1
Read 17.1 on pp 192-193
Address each of the learning objectives on p.
192 by taking notes that directly relate to the
objectives.
Due on __________________