HONORS CHEMISTRY - CHAPTER 8 NAME: COVALENT BONDS DATE: VAN DER WAALS FORCES WKST # 1 - ANS - V16 PAGE: THIS SOLUTION KEY WAS ORIGINALLY CREATED BY AN AHC STUDENT, 2007-2008 FOR EACH QUESTION LIST ONLY THE STRONGEST INTERPARTICLE FORCE PRESENT REMEMBER THE COLOR GRID FOR POLARITY Area of Partial Positive Charge Neutral (Switzerland) Area of Partial Negative Charge 1. While C O bonds are polar, carbon dioxide (CO2) is linear and symmetrical, therefore it is nonpolar; H2O, of course, is polar. That means the forces must be dipole-induced dipole. 2. Methane (CH4) has four polar bonds arranged symmetrically in tetrahedral electronic and molecular geometry arrangements; therefore, it is nonpolar and the forces must be London dispersion. 1
3. Rubidium fluoride (RbF) is ionic, while H 2 O is polar. When an ionic substance dissociates it splits up into its constituent cations and anions. That means that the attractive force between either of the ions and the water molecule would be ion-dipole. Note: The blue line in the RbF picture represents one nanometer. 4. Helium (He) is nonpolar, while gaseous hydrogen chloride (HCl) is a dipole. So the forces must be dipole- induced dipole forces. Note: The blue line in the He picture represents one nanometer. 5. Water is a dipole, a water molecule being attracted to another water molecule would look at first to be dipole-dipole. However, hydrogen is bonded to one of the NOF s in the water molecule, so the interparticle forces among the water molecules are hydrogen bonds. 2 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16
6. Ammonia (NH3) has a tetrahedral electronic geometry and a trigonal pyramidal molecular geometry. Since it is not symmetrical, it is polar. Therefore, both water and ammonia are dipoles and in both a hydrogen is bonded to a NOF; therefore, the force must be a hydrogen bond. 7. Because ethanol (C2H5OH or CH3CH2OH) molecules end in an oxygen bonded to a hydrogen, the forces are hydrogen bonds. 8. Calcium chloride (CaCl2) is ionic, but water is polar, so the force is ion-dipole. 3 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16
9. Chloroform or trichloromethane (CHCl 3 ), has tetrahedral electronic and molecular geometries; however, with one C H bond and three C Cl bonds, the molecule is not symmetrical and it is polar. Therefore, the interparticle forces are dipole-dipole. 10. Barium chloride (BaCl 2 ) is an ionic compound and hydrogen fluoride (HF) is a polar substance, so the forces are ion-dipole. 4 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16
11. O2 and N2 are both nonpolar molecules (Remember the diatomics!). All of the intermolecular forces are London dispersion forces. 12. Boron trifluoride (BF3) has three polar bonds arranged symmetrically in trigonal planar electronic and molecular geometries, therefore, it is nonpolar and the forces must be London dispersion. 13. Hydrogen peroxide (H2O2) is nonsymmetrical molecular compound, so it is polar, as is water. Since both contain H O polar covalent bonds, the forces are hydrogen bonds. 5 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16
14. Hydrogen gas (H 2 ) is nonpolar; the forces would be London dispersion. 15. Iodine monofluoride, IF, is polar, so the forces holding them together would be dipole-dipole. 16. Copper (II) sulfate pentahydrate (CuSO 4 H 2 O) is a salt, while water is polar, so the force is ion-dipole. 17. CH 3 Cl has tetrahedral electronic and molecular geometry arrangements. However, with three C H bonds and one C Cl bond, the molecule is not symmetrical; therefore, the interparticle forces are dipole-dipole. 6 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16
18. Since both molecules are nonpolar, the forces would be London dispersion. 19. Argon, Ar, a monatomic molecule, must be nonpolar while gaseous hydrogen bromide, HBr, is polar. So if they come in contact, the forces between them will be dipole-induced dipole. 20. Ammonia (NH 3 ) is polar with a hydrogen covalently bonded to a NOF, therefore, the forces between the molecules must be hydrogen bonds. For Ammonia See Question #6 Above 7 - HC - Chapter 8 - van Der Waals Forces Worksheet #1 - Answers - V16