The quiz next week will be given during your recitation. It will cover material starting with section First Midquarter Exam Monday, Jan 29 6:30-7:48 pm Rooms TBA Chaps 10, 11, 13 Dr. Zellmer’s web site has very useful informationweb site on 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 H 2 O and CO 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 13Properties of Solutions 13.1 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! ← Temp. increases

Using the Clausius-Clapeyron Equation: Tabulate P in atm and T in K; Calculate lnP and 1/T Plot lnP vs 1/T The slope is = - ΔH vap /R The slope!

Phase Diagrams

The Critical Point:

11.55 The normal melting and boiling points of xenon are -112 o C and -107 o C, respectively. Its triple point is at -121 o C and 282 torr, and its critical point is a 16.6 o C and 57.6 atm. (a) Sketch the phase diagram of Xe, showing the four points 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 excellent discussion 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 be interested in. ↓ These are the ones we’ll be 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 by counting the number of times the plane crosses each axis within a unit cell for each direction.

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 section First Midquarter Exam Monday, Jan 29 6:30-7:48 pm Rooms TBA Chaps 10, 11, 13 Dr. Zellmer’s web site has very useful informationweb site on 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. The values of h, k and l are integers whose values are determined as follows: h = 1/(x-intercept)h = a/(1a) = 1 k = 1/(y-intercept)k = b/(1b) = 1 l = 1/(z-intercept)l = c/(  ) = plane The distance between planes is given by the following formula (for an orthorhombic lattice): 1/d 2 = h 2 /a 2 + k 2 /b 2 + l 2 /c 2 For a cubic lattice this reduces to: 1/d 2 = (h 2 + k 2 + l 2 )/a 2 Plane that goes through the origin The next plane is the one used to calculate hkl

X-Ray Powder Pattern 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.

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

Hexagonal close packing (ABABAB…) Cubic close packing (ABCABC..) fac t

Cubic and Hexagonal Close Packing Hexagonal Close Packing (ABAB…) ABAB Stacking ABCABC Stacking Cubic Close Packing (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 + 1/4c Atom 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 B C 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 questions based on these characteristics.

Contrast the MPs and BPs of some materials which are Molecular Solids: C 6 H 6 C 6 H 5 -CH 3 C 6 H 5 -OH MP BP MP of benzene vs that of toluene: Benzene is highly symmetric and planar. Toluene is less 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-packed structure (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-centered cubic lattice (bcc). The edge of the unit cell is 2.86 Ǻ, and the density is 7.92 g/cm 3. 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 answer these questions. Note that 3.0 on the 1/T-axis is equal to 3.0 x 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