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Transcript of The quiz next week will be given during your recitation. It will cover material starting with...
The quiz next week will be given during your recitation.
It will cover material starting with section10.7.
First Midquarter ExamMonday, Jan 29
6:30-7:48 pmRooms TBA
Chaps 10, 11, 13
Dr. Zellmer’s web site has very useful informationon BP data and the use of Excel for Exps. 13 and 17.
11.5 Vapor Pressure• Explaining Vapor Pressure on the Molecular Level, Volatility, • Vapor Pressure, and Temperature; • Vapor Pressure and Boiling Point
11.6 Phase Diagrams• The Phase Diagrams of H2O and CO2
11.7 Structures of Solids• Unit Cells• The Crystal Structure of Sodium Chloride• Close Packing of Spheres
11.8 Bonding in Solids• Molecular Solids• Covalent-Network Solids• Ionic Solids• Metallic Solids
Chapter 13 Properties of Solutions13.1 The Solution Process
• Energy Changes and Solution Formation• Solution Formation, Spontaneity, and Disorder• Solution Formation and Chemical Reactions
(Add slide of C-C eq and plot.)
But, recall, we always prefer straight lines!
ln PH
R TCvap
vap
1
← Temp. increases
O r w ith P the vapor pressu re a t T and P the vapor pressu re a t T
PH
R TC and P
H
R TC
sub trac t to g ive
P PH
R T T
or
P
P
H
R T T
vap vap
vap
vap
,
ln ln
ln ln
ln
1 1 2 2
22
11
2 12 1
2
1 2 1
1 1
1 1
1 1
Using the Clausius-Clapeyron Equation:
Tabulate P in atm and T in K; Calculate lnP and 1/TPlot lnP vs 1/T
The slope is = - ΔHvap /R
The slope!
Phase Diagrams
The Critical Point:
11.55 The normal melting and boiling points of xenon are -112 oC and -107 oC, respectively. Its triple point is at-121 oC and 282 torr, and its critical point is a 16.6 oCand 57.6 atm.
(a) Sketch the phase diagram of Xe, showing the fourpoints given above and indicating the area in which each phase is stable.
(b) Which is more dense, solid or liquid Xe?
(c) If Xe gas is cooled under an external pressure of 100 torr, will it undergo condensation or deposition?
Example Question on Phase Diagrams
11.7 Structures of Solids• Unit Cells• The Crystal Structure of NaCl• Close Packing of Spheres
11.8 Bonding in Solids• Molecular Solids• Covalent-Network Solids• Ionic Solids• Metallic Solids
Sulfur Crystals
Millerite Crystals (a nickel ore)
Some interesting web sites:
Ice and Snow Crystals at Cal Tech web site
See the Carmen site for excellentdiscussion of your XRD Experiment (X-Ray Diffraction experiment)
Univ. of PA discussion of XRD
Youngstown State Univ. XRD Lab
Research Experiences to Enhance Learning (Ohio REEL)
Solids
• We can think of solids as falling into two groups:
– Crystalline—particles are in highly ordered arrangement.
Solids
– Amorphous—no particular order in the arrangement of particles.
These are the ones we’ll beinterested in.
↓
These are the ones we’llbe interested in.
Bravais Lattice Type = P (primitive)
Bravais Lattice Type = I (body centered)
Bravais Lattice Type = F (face centered)
Crystallographic ‘Planes’and Miller Indices
A plane that intercepts the a-axis at a/h,the b-axis at b/k, and the c-axis at c/l is known as an hkl plane, where hkl are the Miller indices.
Alternatively, you can get the Miller indices bycounting the number of times the plane crosseseach axis within a unit cell for each direction.
sin2
and c, b a systems cubicfor that Note
222
lkh
adhkl
Now back to some discussions of unit cells.
The ‘NaCl’ Structure
An alternate view of the NaCl Structure
The quiz next week will be given during your recitation.
It will cover material starting with section10.7.
First Midquarter ExamMonday, Jan 29
6:30-7:48 pmRooms TBA
Chaps 10, 11, 13
Dr. Zellmer’s web site has very useful informationon BP data and the use of Excel for Exps. 13 and 17.
Miller Indices in 3D
In a 3D system there are three Miller Indices, h, k and l. In a 3D system there are three Miller Indices, h, k and l. The values of h, k and l are integers whose values are The values of h, k and l are integers whose values are determined as follows:determined as follows:
h = 1/(x-intercept)h = 1/(x-intercept) h = a/(1a) = 1h = a/(1a) = 1k = 1/(y-intercept)k = 1/(y-intercept) k = b/(1b) = 1k = b/(1b) = 1l = 1/(z-intercept)l = 1/(z-intercept) l = c/(l = c/() = 0) = 0
110 plane110 plane
The distance between planes is The distance between planes is given by the following formula given by the following formula (for an orthorhombic lattice):(for an orthorhombic lattice):
1/d1/d22 = h = h22//aa22 + k + k22//bb22 + + ll22//cc22
For a cubic lattice this reduces For a cubic lattice this reduces to:to:
1/d1/d22 = (h = (h22 + k + k22 + l + l22)/)/aa22
Plane that goes through the origin
The next plane is the one used to calculate hkl
X-Ray Powder Pattern
2020 2020 3030 4040 5050 6060
2-Theta (Degrees)2-Theta (Degrees)
There are many different planes of atoms in a crystal. In an X-ray powder diffraction pattern we see many peaks, each one corresponding to scattering from different planes of atoms. The numbers in the above diagram are called Miller Indices, they identify different planes of atoms
in the crystal.
20 30 40 50 60 702Theta
0
50
100
150
200
250
300
350
Int.
X-Ray Powder Diffraction Pattern (Lead Sulfide, PbS)
Each peak corresponds to scattering from a different set of lattice planes. Two planes are
shown above for PbS, which has the same structure as NaCl.
020 planes
220 planes
Hexagonalclosepacking(ABABAB…)
Cubicclosepacking(ABCABC..)
fact
Cubic and Hexagonal Close Packing
Hexagonal Close Packing Hexagonal Close Packing (ABAB…)(ABAB…)
AABBAABB Stacking Stacking
AABBCCAABBCC Stacking Stacking
Cubic Close Packing Cubic Close Packing (ABCABC…)(ABCABC…)
Coordination Environment (Close Packed Structures)
Hexagonal Close Packing
Each atom has 12 nearest neighbors in both structures
A
B
B
B
A
C
Cubic Close Packing
HCP Unit Cell (ABAB…)
Hexagonal close packed structures adopt a hexagonal unit cell, as shown above. For every lattice point there are two atoms displaced from the lattice point by the following vectors:
Atom 1: 1/3a + 2/3b + 1/4cAtom 2: 2/3a + 1/3b + 3/4c
(a) (b) (c)
CCP Unit Cell (ABCABC…)
Cubic close packed structures adopt a face centered cubic (fcc) unit cell. The layers stack perpendicular to the body diagonal of the unit cell.
(a) (b)
A
B
C
A
A
BC
A
11.7 Structures of Solids• Unit Cells• The Crystal Structure of NaCl• Close Packing of Spheres
11.8 Bonding in Solids• Molecular Solids• Covalent-Network Solids• Ionic Solids• Metallic Solids
Know this table in detail. You will see questionsbased on these characteristics.
Contrast the MPs and BPs of some materials which are Molecular Solids:
C6H6 C6H5-CH3 C6H5-OH
MP 5 -95 43
BP 80 111 182
MP of benzene vs that of toluene: Benzeneis highly symmetric and planar. Toluene isless symmetric and cannot pack as tightly,leading to a lower MP.
Another example of Molecular Solids.
11.59 Aluminum metal crystallizes in a cubic close-packedstructure (face-centered cubic cell).
(a) How many aluminum atoms are in a unit cell?
(b) What is the coordination number of each aluminum atom?
(c) Assume that the aluminum atoms can be represented as spheres. If each Al atom has a radius of 1.43 Å, what is the length of a side (usually called a )of the unit cell?
(d) Calculate the density of Al metal.
11.63 An element crystallizes in a body-centeredcubic lattice (bcc). The edge of the unit cell is 2.86 Ǻ,and the density is 7.92 g/cm3.
a) calculate the atomic weight of the element.
b) assuming the molecules are in contact along the body diagonal, what is the radius of the element?
Use this graph to answerthese questions. Note that 3.0 on the 1/T-axis is equal to 3.0 x 10-3 K-1, where T = 333 K
a) What is the normal boiling point of the liquid?
b) Calculate the heat of vaporization of the
liquid.
Pop Quiz No. 1