1. Liquids and Solids Chapter 16 E-mail: benzene4president@gmail.com
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2. Liquids and Solids – ch. 16

3. Liquids and Solids – ch. 16
1. 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. P
g. H2S n. S8

4. Only for molecules with
Liquids and Solids – ch. 16
Dipole-Dipole
Only for molecules with
dipole moments aka
polar molecules
Hydrogen Bonding
A particularly strong
dipole-dipole
only for molecules
with hydrogen
bonded to O, N or F
London Dispersion Forces

5. Liquids and Solids – ch. 16
2. 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

6. for molecules comparable in size
Liquids and Solids – ch. 16
Relative strength of forces ⇒ Ionic > >> Hydrogen bonding > Dipole-Dipole > Dispersion
for molecules comparable in size
Dispersion Forces
Increase with molecular size
Decrease with the
degree of branching
ex:
As the attractive forces get stronger…
Boiling point ↑
Freezing point ↑
Melting point ↑
Heat of fusion ↑
Heat of vaporization ↑
Viscosity ↑
Surface Tension ↑
Vapor Pressure ↓
Volatility ↓

7. Liquids and Solids – ch. 16

8. Liquids and Solids – ch. 16
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).

9. Liquids and Solids – ch. 16

10. Liquids and Solids – ch. 16 4 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 cell
abc hexagonal alignment of atoms
4. Hexagonal Closest Packed: 6 atoms/unit cell
abab hexagonal alignment of atoms

11. Liquids and Solids – ch. 16 2 Types of closest packing
1. abab – hexagonal closest packed
2. abca – cubic closest packed

12. Liquids and Solids – ch. 16 Counting Atoms in a Cubic Unit Cell
Atom is shared between 2 unit cells
Atom is shared between 8 unit cells
Atom is shared between 4 unit cells

13. Liquids and Solids – ch. 16 Unit Cell
Number of atoms/unit cell – (% by volume)
Coordination Number
Edge Length as a function of atomic radius
Simple Cubic
(52.4%) 6
e = 2r
Body Centered Cubic
(68%) 8
𝑒= 4𝑟 3
(e = 2.309r)
Face Centered Cubic aka Cubic Closest Packed
(74%) 12
𝑒=𝑟 8
(e = 2.828r)
Hexagonal Closest Packed
(74%)
N/A

14. Liquids and Solids – ch. 16
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.

15. Liquids and Solids – ch. 16
5. 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)

16. 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

17. Liquids and Solids – ch. 16
Assume the two-dimensional structure of an ionic compound MxAy is
What is the empirical formula of this ionic compound?

18. Liquids and Solids – ch. 16
8. 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)

19. Liquids and Solids – ch. 16 Ionic Solids
Anions (or the larger ion) will align themselves in the lattice points of the unit cell
Cations (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 rare
b. 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

20. Liquids and Solids – ch. 16
9. 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.

21. 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:
n-type ⇒ impurity has
more valence electrons in a
valence shell with higher energy
than the semiconductor
p-type impurity has
fewer valence electrons in a
valence shell with lower energy
Si has 4 valence electrons
As (the dope)
has 5 valence electrons
Si has 4 valence electrons
B (the dope)
has 3 valence electrons

22. Liquids and Solids – ch. 16 M.O. model illustrating doping
and how it enhances
conductivity
n-type doping
p-type doping

23. Liquids and Solids – ch. 16
10. 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?

24. Liquids and Solids – ch. 16 Liquid Solid pressure Equilibrium lines
temperature
melting
freezing
vaporization
condensation
sublimation
deposition
Liquid
Solid
Equilibrium lines
Gas

25. Liquids and Solids – ch. 16
11. 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.

26. Liquids and Solids – ch. 16
12. The enthalpy of vaporization for water is 44 kJ/mol. What is the boiling point if the atmospheric pressure were 0.33 atm?
ln P2 P1 = −ΔHvap R T2 − 1 T1

27. Liquids and Solids – ch. 16
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)

28. Liquids and Solids – ch. 16 Heating curve for water q = n Δ Hvap
q = n Δ Hfus
q = mcΔT

29. Liquids and Solids – ch. 16
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)

30. Liquids and Solids – ch. 16
You have completed ch.16

31. Liquids and Solids – ch. 16
1. 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 solid
c. NH4Br ⇒ Ionic/Ionic solid
d. F2 ⇒ LDF/Molecular solid
e. CH3OH ⇒ HB/DD/LDF/Molecular solid
f. Ca ⇒ metallic/metallic solid
g. 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

32. 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

33. 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

34. Liquids and Solids – Answer Key
6. The unit cell in the two-dimensional crystal contains 1 X and 1O.
X X X X X
O O O O
Repeating
Unit ⇒ there’s 4
corners where each
corner has 1/8 X
for a
total of ½ X
and the face has
½ 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 has
½ X ⇒ simplify 1/2X:1/2 O is 1:1

35. Liquids and Solids – Answer Key
Assume the two-dimensional structure of an ionic compound MxAy is
Repeating Unit
4 corners with 1/8 of a
cation and 1 cation on
the face or ½ for a total
of 1 cation - all of the
anions are on the face
4x1/2 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

36. 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↓

37. Liquids and Solids – Answer Key
11. Drawing the points of the phase diagram you get…
note: (+) slope T F
760
torr 72
torr 18 °C 21 °C 87 °C

38. 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/ kJ/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)

39. 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

40. Liquids and Solids – Answer Key
-mCΔT = mCsolid Δ T + nHfus +mCliquidΔ T -(180g)(4.18J/g°C)(Tf-64°C) =(25g)(2.03J/g°C)(7°C)+(25g/18g/mol)(6010J/mol)+(25g)(4.18J/g°C)(Tf-0°C) Tf = 46°C