Title: Chemistry 123
1Chemistry 123
2Course info
- http//www.albion.edu/chemistry/abbethune/123/S08/
default.htm
3Think about it
Which phase change occurs in each of the
following (vaporization, condensation,
sublimation, deposition, freezing, melting)
- The water level in an aquarium tank falls
continuously (there is no leak) - vaporization
- A black deposit of tungsten metal collects on the
inside of a light bulb containing a tungsten
filament. - deposition
- Mothballs slowly become smaller and eventually
disappear. - sublimation
- Candle wax turns to liquid under the heat of a
candle flame. - melting (fusion)
- A mixture of scrambled eggs placed in a cold
vacuum chamber slowly turns to a powdery solid. - evaporation
4Think about it
- A cup of room temperature water is placed in a
well-insulated cup. - After some of the water is allowed to evaporate,
it is found that the temperature of the water in
the cup has dropped below the room temperature. - Why?
5Refrigeration phase changes
Inside (refrigerant gas)
Cooling coils
Compressor (gas ? liquid)
outside
Expansion valve (liquid? gas)
http//www.howstuffworks.com/refrigerator4.htm
6DHvap and DHfus for several common substances
7Cooling curve for water
8Vapor pressure temperature
0
9Phase diagram, CO2
10Phase diagram, H2O
http//www.colorado.edu/physics/phys4230/phys4230_
sp02/mainPage5.html
11Cleaning clothes with CO2?
- Liquid carbon dioxide
- Great solvent (maybe too good)
- Cheap
- Abundant supply
12Reading the diagram
- What is the minimum temperature at which carbon
dioxide will be in the liquid phase? - -57C
13Reading the diagram
- At -57C, what is the lowest pressure that could
be used in order to keep CO2 in liquid phase? - 5.1 atm
14Reading the diagram
- It is more energy-efficient to clean clothes at
room temperature (25C). - Will this require a higher or lower pressure of
CO2 than T -57C? - A higher pressure will be required (5 atm lt P lt
73 atm)
15Application
- Beyond the critical point, a supercritical fluid
(sc) exists. - What is the max temperature and pressure at which
the CO2 cleaning system could be used while still
avoiding the scCO2 phase. - T lt 31CP lt 73 atm
16Phase diagrams for CO2 H2O
17Pauling electronegativity (EN) scale
18Dispersion (London) Forces
19(No Transcript)
20Intermolecular forces
21Think about it
- Which intermolecular forces exist between CH3Cl
molecules? - dispersion forces
- hydrogen bonding
- dipole-dipole forces
- dipole-induced dipole forces
- ion-induced dipole forces
22Dipole-dipole interaction
0
23Dipole-dipole interactions
24Think about it
- Which intermolecular forces exist between CH3OH
molecules? - dispersion forces
- hydrogen bonding
- dipole-dipole forces
- dipole-induced dipole forces
- ion-induced dipole forces
25Hydrogen bonding and BP
26Hydrogen bonding in water (ice)
27(No Transcript)
28Hydrogen bonding in DNA
29Think about it
- Indicate the strongest intermolecular force that
exists between H2O molecules and benzene
molecules (C6H6)? - dispersion forces
- hydrogen bonding
- ion-dipole forces
- dipole-induced forces
- ion-induced dipole forces
30Think about it
- Indicate the strongest intermolecular force that
exists between CH3CH3 molecules and Na? - dispersion forces
- hydrogen bonding
- ion-dipole forces
- dipole-induced forces
- ion-induced dipole forces
31Think about it
- Indicate the strongest intermolecular force that
exists between H2O molecules and Na? - dispersion forces
- hydrogen bonding
- ion-dipole forces
- dipole-induced forces
- ion-induced dipole forces
32Think about it
- Which of the following would you expect to be the
most polarizable? - Ca2
- K
- Ar
- Cl-
- S2-
33Think about it
- Consider HF and H2O. These two molecules are
both polar (HF has a larger dipole moment) and
the same number of electrons. - Why does water boil at a much higher temperature
than HF?