Chapter 11 IMFs, LIQUIDS, & SOLIDS
 Difference between solid, liquid, gas
 Intermolecular Forces (IMF) control melting point, boiling point, vapor pressure,
viscosity.
 Van der Waals forces =
- Dispersion forces occurs in between all molecules, polar or not. Caused
by the motion of electrons which might result in temporary dipole and it
will induce a dipole on its neighbor.
- Shape and mass are factors in strength of dispersion forces.
- Dipole-Dipole between molecules with permanent dipole. Oppositely
charged ends of neighboring molecules attract each other.
- Degree of polarity is a factor in strength of dipole-dipole forces.
- Hydrogen Bonding between molecules with H-F, H-O or H-N bonds.
 Ion – Dipole interactions important in solutions
 Viscosity increases with stronger IMF and decreases with temperature
 6 Phase changes, know names and endo or exothermic
 Heat of fusion, heat of vaporization
 Heat curve q=mHf q=mHv q=mcΔT
 Vapor pressure increases with temperature
 When vapor pressure = atmospheric pressure, liquid boils.
 Normal BP = @ Standard Pressure
 In ionic solids ions pack themselves in a way to minimize repulsive forces and maximize
attractive forces
 Types of solids =
- Ionic, between ions (usually metal & nonmetal), hard, high MP, poor
conductors
- Metallic, metal atoms, soft or hard, high MP, good conductors
- Covalent molecular, molecules connected via IMF, soft, low MP, poor
conductors
- Covalent network, atoms or molecules connected with covalent bonds
(macromolecule), very hard, very high MP, variable conductivity
IMF PRACTICE
1. Which of the following actions would be likely to change the boiling point of a sample of a pure liquid in
an open container?
I. Placing it in a smaller container
II. Increasing the number of moles of the liquid in the container
III. Moving the container and liquid to a higher altitude
(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II, and III
Questions 2-5 refer to the following descriptions of bonding in different types of solids.
(A) Lattice of positive and negative ions held together by electrostatic forces
(B) Closely packed lattice with delocalized electrons throughout
(C) Strong single covalent bonds with weak intermolecular forces
(D) Strong multiple covalent bonds (including bonds.) with weak intermolecular forces
(E) Macromolecules held together with strong polar bonds
2. Cesium chloride, CsCl (s)
3. Gold, Au(s)
4. Carbon dioxide, CO2(s)
5. Methane, CH4(s)
Questions 6-7 relate to the graph shown on the right. The graph shows the temperature of a pure substance as it
is heated at a constant rate in an open vessel at 1.0 atm pressure. The substance changes from the solid to the
liquid to the gas phase.
6. The substance is at its normal freezing point at time…
15. (A) t1 (B) t2 (C) t3
(D) t4
(E) t5
7. Which of the following best describes what happens to the
substance between t4 and t5?
(A) The molecules are leaving the liquid phase.
(B) The solid and liquid phases coexist in the equilibrium.
(C) The vapor pressure of the substance is decreasing.
(D) The average intermolecular distance is decreasing.
(E) The temperature of the substance is increasing.
8. The best explanation for the fact that diamond is extremely hard is that diamond crystals…
(A) are made up of atoms that are intrinsically hard because of their electronic structures
(B) consist of positive and negative ions that are strongly attracted to each other
(C) are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms
(D) are formed under extreme conditions of temperature and pressure
(E) contain orbitals or bands of delocalized electrons that belong not to single atoms but to each crystal as a
whole
9. Sodium chloride is LEAST soluble in which of the following liquids?
(A) H2O (B) CCl4 (C) HF (D) CH3OH (E) CH3COOH
10. Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a
liquid to a vapor?
(A) H-O bonds break as H-H and O-O bonds form.
(B) Hydrogen bonds between H2O molecules are broken.
(C) Covalent bonds between H2O molecules are broken.
(D) Ionic bonds between H+ ions and OH− ions are broken.
(E) Covalent bonds between H+ ions and H2O molecules become more effective.
11. Of the following pure substances, which has the highest melting point?
(A) S8 (B) I2 (C) SiO2 (D) SO2 (E) C6H6
12. Which of the following statements is false?
a. Condensed states have much higher densities than gases.
b. Molecules are very far apart in gases and closer together in liquids and solids.
c. Gases completely fill any container they occupy and are easily compressed.
d. Vapor refers to a gas formed by evaporation of a liquid or sublimation of a solid.
e. Solid water (ice), unlike most substances, is denser than its liquid form (water).
13. Ten (10.0) moles of a gas are contained in a 10.0 L container at 273 K. Calculate the pressure of the gas.
a. 2.24 atm
b. 4.48 atm
c. 11.2 atm
d. 15.7 atm
e. 22.4 atm
14. A mixture of gas consists of 5.0 g CH4, 5.0 g C2H2, and 5.0 g C2H4. What are the mole fractions of each?
XCH4 XC2H2 XC2H4
a. 0.321 0.192 0.177
b. 0.333 0.333 0.333
c. 0.217 0.375
d. 0.567 0.137
e. 0.457 0.281
0.408
0.326
0.262
15. A 5.00 L container contains CH4, H2, and Xe at 35 C with a total pressure of 1.81 atm. If there are equal moles of
each gas, what is the partial pressure of H2?
a. 0.603 atm
b. 0.034 atm
c. 1.81 atm
d. 3.05 atm
e. 0.362 atm
16. What is the pressure exerted by a mixture of 1.0 g H2 and 5.0 g He when confined to a volume of 5.0 liters at
20. C?
a. 12.6 atm
b. 8.4 atm
c. 3.61 atm
d. 10.4 atm
e. 6.5 atm
17. Which one of the following statements is not consistent with the kinetic-molecular theory?
a. The volume occupied by the molecules (only) of a gas becomes significant only at very low pressures.
b. A given sample of a gas is mostly empty space except near the liquefaction point.
c. Except near the liquefaction point, the attractive forces between molecules of a gas are very small.
d. Collisions between the molecules of a gas are elastic.
e. The attractive forces between the molecules of a gas become significant only at very low temperatures.
18. In terms of energy and entropy, systems in nature tend to favor changes that lead to
a. higher energy and higher entropy
b. higher energy and lower entropy
c. lower energy and higher entropy
d. lower energy and lower entropy
19. The boiling points of the halogens increase in the order F2 < Cl2 < Br2 < I2 due to the resulting increasing
__________ interactions.
a. ion-dipole
b. hydrogen-bonding
c. ion-ion
d. dispersion forces
e. permanent dipole-dipole
20. Calculate the amount of heat (in joules) required to convert 92.5 g of water at 25.0 C to steam at 108.0 C.
(Sp. heat of H2O(l) = 4.18 J/g• C, Sp. heat of H2O(g) = 2.03 J/g• C, heat of vap. of H2O(l) = 2.260 kJ/g)