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Transcript of Liquids and Solids Chapter 16 E-mail: [email protected]@gmail.com...
Liquids and SolidsChapter 16E-mail: [email protected]
Web-site: http://clas.sa.ucsb.edu/staff/terri/
Liquids and Solids – ch. 161. Indicate the types of forces present and the type of solid for each of
the following substances:a. CCl4 h. KOH
b. HF i. BH3
c. NH4Br j. H2CO
d. F2 k. SiO2
e. CH3OH l. Ar
f. Ca m. Pg. H2S n. S8
Liquids and Solids – ch. 16London Dispersion ForcesHydrogen Bonding
A particularly strongdipole-dipole
only for moleculeswith hydrogen
bonded to O, N or F
Dipole-DipoleOnly for molecules with
dipole moments aka polar molecules
Liquids and Solids – ch. 162. Using intermolecular forces predict the following:
a. highest melting point F2 or Br2
b. highest melting point HF or HCl
c. highest boiling point HOCH2CH2OH or CH3CH2OH
d. highest boiling point CH3CH3 or CH3CH2CH3
e. highest vapor pressure CH3CH2OH or CH3OCH3
f. highest vapor pressure CCl4 or CH2Cl2
g. highest freezing point MgO or H2O
h. highest surface tension C14H30 or C24H50
Liquids and Solids – ch. 16
Relative strength of forces ⇒ Ionic > >> Hydrogen bonding > Dipole-Dipole > Dispersionfor molecules comparable in size
Dispersion Forces1. Increase with molecular size2. Decrease with the degree of branching ex:
As the attractive forces get stronger…1. Boiling point ↑2. Freezing point ↑3. Melting point ↑4. Heat of fusion ↑5. Heat of vaporization ↑6. Viscosity ↑7. Surface Tension ↑8. Vapor Pressure ↓9. Volatility ↓
Liquids and Solids – ch. 163. Copper has an inter-planar spacing of 1.36 Å. Calculate the
wavelength of the X ray that should be used if θ is 15° (assume n=1).
Liquids and Solids – ch. 164 Types of Unit Cells for Metallic solids
1. Simple Cubic: 1 atom/unit cell
2. Body-centered Cubic: 2
atoms/unit cell
3. Face-centered Cubic or Cubic
Closest Packed: 4 atoms/unit cellabc hexagonal alignment of
atoms
4. Hexagonal Closest Packed: 6
atoms/unit cellabab hexagonal
alignment of atoms
Liquids and Solids – ch. 16
2 Types of closest packing 1. abab – hexagonal closest packed
2. abca – cubic closest packed
Liquids and Solids – ch. 16
Counting Atoms in a Cubic Unit Cell
Atom is shared between 4 unit cells
Atom is shared between 2 unit cells
Atom is shared between 8 unit cells
Liquids and Solids – ch. 16
Unit CellNumber of
atoms/unit cell – (% by volume)
Coordination Number
Edge Length as a function of atomic
radius
Simple Cubic 1 (52.4%) 6 e = 2r
Body Centered Cubic
2 (68%) 8(e = 2.309r)
Face Centered Cubic aka Cubic Closest Packed
4 (74%) 12(e = 2.828r)
Hexagonal Closest Packed 6 (74%) 12 N/A
Liquids and Solids – ch. 164. Zinc crystallizes in a cubic closest packed structure. The radius of a
zinc atom is 135 pm. Calculate the density in g/mL for solid zinc.
Liquids and Solids – ch. 165. Titanium metal has a body-centered cubic unit cell. The density is
4.50 g/cm3. Calculate the atomic radius in angstroms of titanium. (1010Å= 1m)
Liquids and Solids – ch. 16
6. The unit cell in this two-dimensional crystal contains __________ Xs and __________ Os.
a. 1, 1 b. 2, 1 c. 1, 2 d. 4, 1 e. 1, 4
Liquids and Solids – ch. 16
7. Assume the two-dimensional structure of an ionic compound MxAy is
What is the empirical formula of this ionic compound?
Liquids and Solids – ch. 168. Consider the following cubic closest packed structures. For each
compound determine where the ions are in the lattice.
a. NaCl (Na+ = 95 pm, Cl– = 181 pm )
b. ZnS (Zn2+= 74 pm, S2– = 184 pm)
c. CaCl2 (Ca2+ = 99 pm, Cl– = 181 pm)
Liquids and Solids – ch. 16
Ionic SolidsAnions (or the larger ion) will align themselves in the
lattice points of the unit cellCations (or the smaller ion) will occupy the holes created
by the lattice points
In FCC aka CCP lattices there are 3 types of holes:a. Trigonal holes are occupied when the radius of the
cation is less than 22% of the anion – very rareb. Tetrahedral holes (8 available) are occupied when the
radius of the cation is between 22% and 41% of the anion
c. Octahedral holes (4 available) are occupied when the radius of the cation is between 41% and 73% of the anion
Liquids and Solids – ch. 169. Identify the type of doping in each of the following.
a. Gallium doped with tin
b. Antimony doped with germanium
c. A material is made from Al, Ga, and As. The mole fractions of these elements are 0.25, 0.26, and 0.49, respectively.
Liquids and Solids – ch. 16
Doping ⇒enhancing the conductivity
of a semiconductor by adding a trace amount of an impurity (aka the dope)
2 Different Types of doping:a. n-type impurity has ⇒ more valence electrons in a valence shell with higher energy than the semiconductorb. p-type impurity has fewer valence electrons in a valence shell with lower energy than the semiconductor
Si has 4 valence electrons
As (the dope) has 5 valence electrons
Si has 4 valence electrons
B (the dope) has 3 valence electrons
Liquids and Solids – ch. 16
M.O. modelillustrating doping
and how it enhancesconductivity
n-type doping p-type doping
Liquids and Solids – ch. 1610. Consider the following phase diagrams for water and carbon
dioxide respectively – which phase is the most dense for each substance? How does pressure affect the MP and BP for each substance?
Liquids and Solids – ch. 16pr
essu
re
temperature
melting
freezing
vaporization
condensation
sublimation
deposition
Liquid
Solid
Gas
Equilibrium lines
Liquids and Solids – ch. 1611. Pure compound Z has a triple point at 18 ° C and 72 torr, a normal
melting point at 21 °C, and a normal boiling point at 87 °C. Which of the following statements regarding compound Z is/are correct?
a. The density of the solid is greater that that of the liquid.
b. Sublimation occurs if starting with a solid at a constant temperature of 17 °C the pressure is decreased until a phase change occurs.
c. Condensation occurs if the temperature is decreased from
55 °C to 13 °C at a constant pressure of 1.00 atm.
Liquids and Solids – ch. 1612. The enthalpy of vaporization for water is 44 kJ/mol. What is the
boiling point if the atmospheric pressure were 0.33 atm?
ln =
Liquids and Solids – ch. 1613. How much heat does is required to take 10 g of ice at -31 °C to
vapor at 155 °C? (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02 J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Liquids and Solids – ch. 1614. Determine the final temperature if a 25 g cube of ice at -7 °C is
placed in 180 mL of water at 64 °C and allowed to come to equilibrium. (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02 J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Liquids and Solids – ch. 161. Indicate the types of forces present and the type of solid for each of
the following substances:a. CCl4 LDF/Molecular solid⇒b. HF ⇒ HB/DD/LDF/Molecular solidc. NH4Br Ionic/Ionic solid⇒d. F2 LDF/Molecular solid ⇒e. CH3OH HB/DD/LDF/Molecular solid⇒ f. Ca ⇒ metallic/metallic solidg. H2S ⇒ DD/LDF/Molecular solid h. KOH Ionic/Ionic solid⇒i. BH3 LDF/Molecular solid⇒j. H2CO ⇒ DD/LDF/Molecular solid k. SiO2 Covalent Network solid⇒l. Ar LDF/Atomic solid⇒m. P Covalent Network solid⇒n. S8 LDF/Molecular solid
Liquids and Solids – Answer Key
2. Using intermolecular forces predict the following:
a. Br2 b. HF c. HOCH2CH2OH d. CH3CH2CH3 e. CH3OCH3
f. CCl4 g. MgO h. C24H50
3. Copper has an inter-planar spacing of 1.36 Å. Calculate the wavelength of the X ray that should be used if θ is 15° (assume n=1).
nλ=2dsinθ ⇒ (1)(λ)=2(1.36 Å)(sin 15°) ⇒ λ = 0.70 Å or 0.07nm
Liquids and Solids – Answer Key
4. Zinc crystallizes in a cubic closest packed structure. The radius of a zinc atom is 135 pm. Calculate the density in g/mL for solid zinc.
D = mass/volume ⇒ since cubic closest packed has 4 atoms per unit cell ⇒ mass of unit cell = 4(65.39amu)(1g/6.022x1023amu) = 4.34x10-22g
The volume of the unit cell is edge3 ⇒ e3=(2.828(1.35x10-8cm)) 3 ⇒ 5.57x10-
23cm3
D = (4.34x10-22g)/(5.57x10-23cm3) = 7.8g/cm3
5. Titanium metal has a body-centered cubic unit cell. The density is 4.50 g/cm3. Calculate the atomic radius of titanium. Body centered cubic has 2 atoms per unit cell ⇒ mass of unit cell = 2(47.88amu)(1g/6.022x1023amu) = 1.59x10-22g ⇒ volume = m/d ⇒ volume = (1.59x10-22g)/(4.5g/cm3) = 3.53x10-23 cm3 ⇒ edge = (3.53x10-23 cm3 )1/3 = 3.29x10-8cm or 329pm ⇒ radius = 329pm/2.309 = 142pm
6. The unit cell in the two-dimensional crystal contains 1 X and 1O.
X X X X X
O O O O
X X X X X
O O O O
X X X X X
Liquids and Solids – Answer Key
Repeating Unit there’s 4⇒corners where eachcorner has 1/8 X for a total of ½ Xand the face has½ O simplify ⇒1/2X:1/2 O is 1:1
Repeating Unit there’s 4 corners where⇒each corner has 1/8 O for a total of ½ O and the face has½ X simplify 1/2X:1/2 O is 1:1⇒
Liquids and Solids – Answer Key
7. Assume the two-dimensional structure of an ionic compound MxAy is
Repeating Unit4 corners with 1/8 of acation and 1 cation onthe face or ½ for a totalof 1 cation - all of the anions are on the face4x1/2 is 2 anions
What is the empirical formula of this ionic compound? MX2
Smaller ion is most likely to be the cation
Larger ion is most likely to be the anion
Liquids and Solids – Answer Key
8. Compare the cubic closest packed structures for NaCl (radius of Na+ = 0.66 radius of Cl-), ZnS (radius of Zn2+ = 0.35 radius of S2-) and CaCl2 (radius of Ca2+ = 0.68 radius of Cl-).
NaCl => Na+ will fill all of the octahedral holes
ZnS => Zn2+ will fill all of the ½ of the tetrahedral holes
CaCl2 => Ca2+ will fill ½ of the octahedral holes
9. Identify the type of doping in each of the following.
a. Ga/Sn => n-type b. Si/B => p-type
10. When the solid/liquid line has a positive slope the solid is most dense phase (more typical) and as P ↑ MP ↑ – however if the solid/liquid line has a negative slope the liquid is most dense (rare) and as P ↑ MP↓
Liquids and Solids – Answer Key
11. Drawing the points of the phase diagram you get…
a. Tb. Tc. F
note: (+) slope
760torr
72torr
18°C
21°C
87°C
Liquids and Solids – Answer Key
12. The enthalpy of vaporization for water is 44 kJ/mol. What is the boiling point if the atmospheric pressure were 0.33 atm? Since we know that the BP of water at 1 atm is 100°C we can figure out the BP at all other pressures using the ΔHvap
ln(P1/P2) = (ΔHvap/R)(T2-1 – T1
-1)
ln(0.33atm/1atm) = (44kJ/mol/0.008314kJ/molK)(T2-1 – 373-1K)
T2 = 405K
13. How much heat does is required to take 10 g of ice at -31 °C to vapor at 155 °C? (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02 J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
This is a 5 step process => 3 changes in temperature (q=mC Δ T) and 2 phase changes (q=n ΔH)
Liquids and Solids – Answer Key
q1=(10g)(2.03 J/g°C)(+31°C) = 629.3J or 0.629kJ
q2=(10g/18g/mol)(6.01kJ/mol) = 3.34kJ
q3=(10g)(4.18 J/g°C)(+100°C) = 4180J or 4.18kJ
q4=(10g/18g/mol)(40.7 kJ/mol) = 22.6kJ
q5=(10g)(2.02 J/g°C)(+55°C) = 1.11kJ
qtotal = 31.86kJ
14. Determine the final temperature if a 25 g cube of ice at -7 °C is placed in 180 mL of water at 64 °C and allowed to come to equilibrium. (Csolid = 2.03 J/g°C , Cliquid = 4.18 J/g°C , Cgas = 2.02 J/g°C, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.7 kJ/mol)
Heat is transferred from the hot water into the cold water
-qhot = +qcold