spano velasco (ds28282) – hw 01 – Fakhreddine – (52395) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 1.0 points For which of the molecules A) O 2 B) CO 2 C) SO 2 D) O 3 will dipole-dipole interactions be important? 1. B and D only 2. A and D only 3. A and C only 4. Another combination of compounds 5. B and C only 6. None has dipole-dipole interactions. 7. C and D only correct 8. A and B only 9. All have dipole-dipole interactions. Explanation: O 2 and CO 2 do not have dipole moments. 002 1.0 points Which of the following can form intermolecu- lar hydrogen bonds? 1. AsH 3 2. CH 3 CH 2 CH 2 CH 2 CH 3 3. CH 3 OCH 3 4. HBr 5. CH 3 OH correct Explanation: Only molecules with H attached to the elec- tronegative atoms N, O, and F can hydrogen bond. Of the molecules given only CH 3 OH has the H directly bonded to O, so it can undergo hydrogen bonding. 003 1.0 points What types of intermolecular interactions does ammonia (NH 3 ) exhibit? I) instantaneous dipole or van der Waals II) dipole-dipole III) hydrogen bonding IV) covalent bonding 1. I, II, and III only correct 2. I only 3. II and IV only 4. II only 5. II and III only 6. I and II only Explanation: All molecules, because they have elec- tron clouds, experience instantaneous dipoles. NH 3 is polar and thus experiences dipole-dipole interactions. NH 3 contains N Hbonds and therefore experiences hy- drogen bonding interactions. Covalent bond- ing is an intramolecular interaction. 004 1.0 points In which of these compounds would you find ONLY dispersion forces existing between the molecules? I. CCl 4 ; II. CO 2 ; III. HBr; IV. NH 3 . 1. III only 2. I and IV only 3. IV only 4. II and IV only 5. II and III only
spano velasco (ds28282) – hw 01 – Fakhreddine – (52395) 2 6. I and II only correct 7. I only 8. III and IV only 9. I and III only 10. II only Explanation: A nonpolar covalent molecule would have only dispersion forces with another nonpolar covalent molecule. 005 1.0 points Consider four molecules I) CHCl 3 II) CH 4 III) CH 3 Cl IV) CCl 4 Which of these exhibit permanent dipole- dipole interactions? 1. I, III, and IV only 2. I only 3. None of these 4. I and III only correct 5. III only Explanation: Dipole-dipole interactions occur in polar molecules. CHCl 3 and CH 3 Cl are polar be- cause their dipole moments do not cancel. CH 4 and CCl 4 are symmetric; their dipole moments cancel and the overall molecule is non-polar. 006 1.0 points What is the strongest evidence for hydrogen bonding? 1. Hydrogen is able to accept or donate elec- trons, so it is the most versatile atom in the periodic chart. 2. Hydrogen has an extremely low elec- tronegativity. 3. The boiling points of NH 3 , H 2 O, and HF are abnormally high compared with the rest of the hydrides in their respective periods.