Molecular Structure: the VSEPR
Model
Valence Shell electron-pair repulsion
VSEPR model
Useful to predict geometry of a molecule
Postulate:
The structure around an atom is
determined by minimizing e
3. Factors affecting solubility
A. Structural effects
As discussed earlier, molecular structure determines the
polarity.
The solubility is governed by interactions between the solute
and the solvent.
11/17/2013
Zumdahl Chapter 11
Solutions
Define: SOLUTION a homogeneous mixture of two or more
substances that do not enter in a chemical reaction.
SOLVENT dissolving medium
SOLUTE any component
diss
Evaporation
8. Vapor pressure and Changes of state
Kinetic energy of the liquid molecules at the surface are not all
the same (distribution).
When the kinetic energy of a given molecule overcomes th
Zumdahl Chapter 10
Liquids and Solids
GASES
SOLIDS
Fluid
Dense
Compressible
Incompressible
Have low density
Anisotropic
Completely fill container
Isotropic
Different atomic
environments of the
10/20/2013
Forms of expressing the Ideal Gas Law:
Keep n constant:
PV
= const.
T
PV = n R T
PV1 P2V2
1
=
=L
T1
T2
Keep T constant:
PV
= const.
n
P1 1 PV 2
V
= 2 =L
n1
n2
Keep P constant:
V
= const
9/29/2013
Sample Exercise 8.8: ClF3, XeO3, RnCl2, BeCl2, ICl4
12. Resonance
Sometimes, more than one valid Lewis structure is possible for
a given molecule.
Consider the nitrate ion, NO3 (5 + 63 + 1 =
6. Routes for calculating the free energy change in
chemical reactions
A.From G = H T S:
Example 17.9: Consider thee reaction:
2SO2 (g) + O2 (g)
2SO3 (g)
Calculate H , S and G:
Substance
!
H !f (kJ/m
Introduction:
Basic Definitions in Thermodynamics ( ics)
System part of the universe
of special interest, or under
investigation.
Surroundings remainder of
the universe around the
system.
Boundary
Molecular Structure: the VSEPR
Model
Valence Shell electron-pair repulsion
VSEPR model
Useful to predict geometry of a molecule
Postulate:
The structure around an atom is
determined by minimizing e
A tube with a bulb at the
end that is covered by a
semipermeable membrane.
The normal flow of
solvent into the solution
(osmosis) can be
prevented
by applying an external
pressure to the solution.
The
Quantum Numbers n,l,ml:
n = 1 l = 0 l = 0 therefore ml = 0 Giving 1s or 1,0,0 or 1s orbital
n = 1 has 1 orbital
n = 2 l = 0, 1 l = 0 therefore ml = 0 Giving 2s or 2,0,0 or 2s orbital
l = 1 therefore m
Free Energy (Symbol: G)
G = H - TS
G = H TS
(from the standpoint of the system)
Divide by T:
G/T = H/T S
= Ssurr -S (constant T and P)
= SUniverse
+Suniv = -G
T
A process (at constant T, P) is spontan
Zumdahl Chapter 7
Atomic Structure and Periodicity
1. The nature and properties of waves:
Wavelength distance between two
peaks or troughs. ()
Frequency number of cycles that
pass through a given poin
11/19/2013
6. Routes for calculating the free energy change in
chemical reactions
This section will be covered in this weeks recitation sessions.
7. Dependence of free energy on pressure
Equilibrium p
5. Entropy changes in chemical reactions:
2nd Law:
for a spontaneous process:
Suniv. > 0
Gsys. < 0
We applied those forms to physical processes
such as changes of state and formation of
solutions.
Ent
Sample 17.3: Order in living cells is spontaneous: large
molecules assemble from simple ones.
Note that Ssys. < 0 .
Ssys. + Ssurr.
<0
Suniv. > 0
>0
but |Ssurr.| > |Ssys.|
3. Effect of temperature on s
Apolar molecules could contain polar bonds but, the net dipole
moment is zero.
AB2
CO2
AB4
AB3
BF3
SO3
CH4
CCl4
6. Partial Ionic Character of Covalent Bonds:
Dipolar molecule: electrons are not shared
6. Routes for calculating the free energy change in
chemical reactions
A.From G = H T S:
Example 17.9: Consider thee reaction:
2SO2 (g) + O2 (g)
2SO3 (g)
Calculate H , S and G:
Substance
o
H of (kJ/m
10/20/2013
7. Effusion and Diffusion
A. Effusion
Define: Effusion Passage of gas molecules through a tiny
orifice into an evacuated chamber (vacuum).
Consider the following Effusion Apparatus:
Probab
Zumdahl Chapter 5
Gases
General Properties:
1. They uniformly fill any container
2. They are compressible
3. They mix in almost all proportions
4. They are less dense than liquids and solids
5. They e
9/29/2013
Sample Exercise 8.8: ClF3, XeO3, RnCl2, BeCl2, ICl4
12. Resonance
Sometimes, more than one valid Lewis structure is possible for
a given molecule.
Consider the nitrate ion, NO3 (5 + 63 + 1 =
e tiny moving light. The more a point is visited, the higher the
intensity at that point.
Radial probability distribution (rpd)
If we slice the e density region into layers like in an onion,
each laye
Orbital Shapes and Energies
s orbitals
all have l = 0
zero angular momentum
spherically symmetrical
(n 1) nodes for each
orbital
All have non-zero probability
at the nucleus
1s 1,0,0
2s 2,0,0
3s 3,0,0