CHM134 General Chemistry I Examination 4, Fall 2008 – Dr. Steel Name 1. Calculate the heat transferred in the following reaction (ΔHrxn). Indicate which direction (exothermic or endothermic) the heat is transferred. (5 points) H H Cl Cl + C C Cl F F F C C H H Cl F 2. Assign formal charges to the elements in each of the structures below and enter the results in the boxes below each structure. Based on your assigned formal charges, circle the structure that makes the greatest contribution to the correct structure of CNO-. (10 points) A B C Formal Charge C N O 3. Draw a Lewis structure for CH3CN that obeys the octet rule for all atoms. Include resonance forms if necessary. (5 points) 4. Draw two non-equivalent Lewis structures for BrO3-. Based on your structures, which makes the greatest contribution to the correct structure of BrO3-? (5 points) 5. In the first column, draw a Lewis Dot structure for each species. In the second column, provide a 3D sketch of the species that includes estimated bond angles and the name of the shape. (24 points) LEWIS DOT STRUCTURE CH4 (example) VSEPR Sketch H H 109.5 o H C H C H H H H shape name: NH3 shape name: CO2 shape name: SF4 shape name: BF3 shape name: tetrahedral 6. From the list below, circle which molecules are linear. (6 points) H2O XeCl2 CS2 SO2 BeCl2 CH4 7. From the list below, circle which molecules are polar (having a non-zero dipole moment). (6 points) CH4 H2O SF4 PCl5 SF6 NCl3 8. Using periodic trends, place the following bonds in order of increasing ionic character. (2 points) S-F Se-F O-F 9. From the list below, circle which molecules contain pure covalent bonds. (6 points) NaCl PF3 Cl2 H2O H2 LiH 10. From the list below, circle which atoms can form compounds with expanded octets. (6 points) N Be S Br O He 11. Consider the molecule below. Determine the hybridization at each of the numbered carbons. Also, indicate the total number of sigma and pi bonds on the structure, respectively. (8 points) C2 C1 sigma bonds pi bonds 12. A molecule whose center has sp3d2 hybridization falls into which electron pair geometry family? (2 points) Use the molecular orbital diagram shown to answer the questions below. 13. What is the bond order of the O22+ ion? (3 points) 14. Circle any species that will be diamagnetic. (5 points) O22+ O21+ O2 O21- O22- 15. What is the bond order of the F2 molecule? (3 points) 16. For the series of species below, which has the shortest bond length and which has the longest bond length? (4 points) F22+ F21+ F2 F21-