Review - 7 Bonding

AP chem Review - 7 Name: ____________________ Text: chapters 8 & 9 (Bonding) © S. O’Malley 2012 • molecular geometries • σ and π bonding • bond lengths • polar vs nonpolar • Lewis structures • hybridization (sp3 , sp2 , sp, sp3 d sp3 d2 ) PROBLEMS 1. VSEPR predicts an SbF5 molecule will be which of the following shapes? a. Tetrahedral b. Trigonal bipyramidal c. Square pyramid d. Trigonal planar e. Square planar 2. The shortest bond would be present in which of the following? a. I2 b. CO c. CCl4 d. O2 2- e. SCl2 3. Which of the following does not have one or more π bonds? a. H2O b. HNO3 c. O2 d. N2 e. NO2 - 4. Which of the following is polar? a. SF4 b. XeF4 c. CF4 d. SbF5 e. BF3 5. Resonance is needed to describe bonding in which of the following? a. H2O b. ClF3 c. HNO3 d. CH4 e. NH3 For 6 – 7: a. ionic bonds b. hybrid orbitals c. resonance structures d. hydrogen bonding e. van der Waals attractions 6. An explanation of the equivalent bond lengths of the nitrite ion is: 7. Most organic substances have low melting points. This may be because, in most cases, the intermolecular forces are: 8. Which of the following has more than one unshared pair of valence electrons on the central atom? a. BrF5 b. NF3 c. IF7 d. ClF3 e. CF4 9. What is the expected hybridization of the central atom in a molecule of TiCl4? This molecule is tetrahedral. a. sp3 d2 b. sp3 d c. sp d. sp2 e. sp3 10. The following set does not include which of the following geometries? SiCl4, BrF4 - , C2H2, TeF6, NO3 - a. Square planar b. Tetrahedral c. Octahedral d. Trigonal pyramidal e. Linear 11. The only substance below that contains ionic, σ, and π bonds is: a. Na2CO3 b. HClO2 c. H2O d. CO2 e. NaCl For 12 – 14: a. C2 b. F2 c. B2 d. O2 e. Ne2 12. The paramagnetic molecule with a bond order of two. 13. The diamagnetic molecule with no antibonding electrons. 14. The paramagnetic molecule with antibonding electrons. 15. The electron pairs point toward the corners of which geometric shape for a molecule with sp2 hybrid orbitals? a. Trigonal planar b. Octahedron c. Trigonal bipyramid d. Trigonal pyramid e. Tetrahedron 16. Regular tetrahedral molecules or ions include which of the following? i. CH4 ii. SF4 iii. NH4 + a. i, ii and iii b. i and iii c. i only d. i and ii only e. ii only 17. Which molecule or ion in the following list has the greatest number of unshared electrons around the central atom? a. CF4 b. ClF3 c. BF3 d. NH4 + e. IF5 18. Which of the following molecules is the least polar? a. PH3 b. CH4 c. H2O d. NO2 e. HCl 19. What types of hybridization of carbon are in the compound 1,3- butadiene, CH2CHCHCH2? i. sp3 ii. sp2 iii. sp a. i and ii b. i, ii, and iii c. i and iii d. i only e. ii only 20. Which of the following molecules is most polar? a. C2H2 b. N2 c. CH3I d. BF3 e. NH3 21. Which of the following processes involves breaking an ionic bond? a. H2 + Cl2 → 2HCl b. I2 → 2I c. Na → Na d. 2C2H6 + 7O2 → 4CO2 + 6H2O e. 2KBr → 2K + Br2 FREE-RESPONSE 22. The nitrite ion, NO2 - , and the nitrate ion, NO3 - , both play a role in nitrogen chemistry. a. Draw the Lewis (electron dot) structure for the nitrite ion and the nitrate ion. b. Predict which ion will have the shorter bond length and justify your prediction. 23. Using Lewis (electron-dot) structures, explain why the ClF3 molecule is polar and the BF3 molecule is not polar. 24. Consider the following substances and their melting points. Explain the relative values of the melting points of these substances. Substance melting point (o C) SrS >2000 KCl 770 H2O 0.00 H2S -85.5 CH4 -182 25. Which of the following tetrafluorides is nonpolar? Use Lewis electron-dot structures to explain your conclusions. SiF4 SF4 XeF4 26. Rank the following compounds in order of increasing melting point. Explain your answer. Lewis electron-dot structures may aid you. SnF2 SeF2 KrF2 27. Use Lewis electron-dot structures to show why the carbon-oxygen bonds in the oxalate ion (C2O4 2- ) are all equal. 28. When PCl5 is dissolved in a polar solvent, the solution conducts electricity. Explain why. Use an appropriate chemical equation to illustrate your answer. 22. a. b. Nitrite has shorter bond lengths. NO2 - has a bond order of 1.5. NO3 - has a bond order of 1.33. 23. In BF3, three bonding pairs and zero nonbonding pairs are on the central atom. It is not polar. However ClF3, with five pairs about the central atom, is polar because of the two lone pairs on the central atom. ClF3 has an asymmetric distribution of charge unlike BF3 which is symmetric. 24. The two compounds with the highest melting point are ionic and the others are molecular. SrS is higher than KCl because the charges on SrS are higher (more lattice energy). H2O is higher than the lower two because of hydrogen bonding. H2S is higher than CH4 because H2S is polar and CH4 is nonpolar. 25. SiF4 and XeF4 are nonpolar. SiF4 is tetrahedral and XeF4 is square planar, both with a symmetric distbution of charge. SF4 is see-saw. 26. KrF2 < SeF2 < SnF2. KrF2 is molecular but nonpolar. SeF2 is molecular but polar. SnF2 is ionic. 27. When you draw out the structure for the oxalate ion, there are many resonance contributors (which all look equivalent in energy) that show the extra π electrons are delocalized. 28. If the solution conducts, PCl5 must ionize. Two acceptable equations are: PCl5 ⇌ PCl4 + + Cl- or 2PCl5 ⇌ PCl4 + + PCl6 - 1. B 2. B 3. A 4. A 5. C 6. C 7. E 8. D 9. E 10. D 11. A 12. D 13. A 14. D 15. A 16. B 17. B 18. B 19. E 20. E 21. E