Chemical Interactions and Properties

1. Which of the following responses arranges interactions in order of increasing strength? ("permanent" is used to indicate non-H-bonding permanent dipole-dipole interactions) covalent bonds, dispersion forces, hydrogen bonds, non-H-bonding permanent dipole-permanent dipole interactions • permanent dipole < dispersion < hydrogen < covalent • hydrogen < permanent dipole < covalent < dispersion • dispersion < hydrogen < permanent dipole < covalent • covalent < hydrogen < permanent dipole < dispersion • hydrogen < dispersion < covalent < permanent dipole

2. Which response includes all of the following substances in which dispersion forces are the most significant factors in determining boiling points, and no other substances? I. Cl2 II. HF III. Ne IV. KNO2 V. CCl4 • I, III, and V • I, II, and III • II and IV • II and V • III, IV, and V

3. Which of the following substances has the weakest "hydrogen bonding" in the liquid state? • HF • NH3 • CH3OH • HCl • H2O

4. Which response contains all the true statements, and no others? I. The vapor pressure of ethyl alcohol increases as temperature increases. II. Liquids of lower molecular weight always exhibit relatively higher vapor pressures than liquids of higher molecular weight. III. A liquid boils at a higher temperature at sea level than on top of a mountain. IV. The temperature of boiling water inside a pressure cooker is above 100°C. • I, III, and IV • I and II • II and IV • III • I and IV

5. If 200. grams of liquid water at 80.°C and 100. grams of water at 10.0°C are mixed in an insulated container, what will the final temperature of the mixture be? (Sp. heat of H2O(l) = 4.18 J/g·°C) • 46.7°C • 60.0°C • 56.7°C • 73.3°C • 45.0°C

6. Which one of the following is not covalent solid? • CO2 • diamond • quartz • graphite • none of these

7. Elemental silicon exists as a solid with a crystal structure like that of diamond. But silicon is less dense than diamond. Which response contains all the correct conclusions that can be drawn? I. Silicon and diamond are allotropes. II. The carbon atoms in diamond are more closely spaced than silicon atoms in solid silicon. III. Silicon is a poor electrical conductor. IV. Silicon is amorphous in the solid state. V. One would expect silicon to have a very high melting point. • II, III, and IV • I and III • II and V • III, IV, and V • II, III, and V

8. Which one of the following elements has the lowest melting point? • Li • Na • K • Rb • Cs

9. For crystal structures that contain only one kind of atom, the nearest neighbors of each atom can be visualized as lying along a line of the unit cell. For a face-centered cubic structure what is the orientation of that line with respect to the unit cell and how many atomic radii does it contain? • cell edge and 2 atomic radii • face diagonal and 4 atomic radii • body diagonal and 3 atomic radii • face diagonal and 2 atomic radii • body diagonal and 4 atomic radii

10. Potassium bromide, KBr, crystallizes in the NaCl (face-centered cubic) lattice. The ionic radii of K+ and Br- ions are 1.33Â and 1.95Â, respectively. Assuming anion-anion contact along the face diagonal and anion-cation contact along the edge of the unit cell, calculate the unit cell edge length, a. • 6.24Â • 6.33Â • 6.56Â • 6.84Â • 7.14Â

11. Potassium bromide, KBr, crystallizes in the NaCl (face-centered cubic) lattice. The ionic radii of K+ and Br- ions are 1.33Â and 1.95Â, respectively. Assuming anion-anion contact along the face diagonal and anion-cation contact along the edge of the unit cell, calculate the density of such a crystal of KBr. • 2.84 g/cm3 • 3.56 g/cm3 • 1.46 g/cm3 • 4.19 g/cm3 • 2.80 g/cm3

12. A certain metal crystallizes in the hexagonal closest-packed structure and has a density of 4.51 g/cm3. Its atomic radius is 1.47Â. There are four atoms per unit cell. Determine its atomic weight. What is the metal? • Ti • Be • Zn • Ir • Sr