μ = q r %ionic character = 1 Debye = 3.34 x 10 30 C m m measured m if 100%ionic 100% Scoring: Six points each for questions 1 through 23; two points each for questions 24 through 32. Directions: n the scantron bubble in your last name, first initial, section number, U-number and. 1
2
1. Draw the best Lewis structure for S3 2-. How many equivalent resonance structures can be drawn? A. 1 B. 2 C. 4 D. 3 E. 8 2. What is the bond order for the N bond in N3 -? N N N A. -1 B. 1 C. 1.33 D. 2 E. 4 3. H molecules have the dipole moment of 1.08D. The percent ionic character of H- bond is 20%. Estimate the bond length of H- bond. The charge of one electron is 1.6 10-19 C. A. 113 nm B. 130 pm C. 206 pm D. 113 pm E. 130 nm 4. Given the molecular orbital diagram below, determine the bond order for nitrogen gas, N2 A. 0 B. 1 C. 2 D. 3 E. 4 3
5. Which of the following is the best Lewis structure for F4 +? Answer:C 6. Determine the Electron Geometry and Molecular Geometry of XeF4. Electron Geometry Molecular Geometry A. Linear Linear B. Tetrahedral Tetrahedral C. Tetrahedral Bent D. Trigonal Bipyramidal Tetrahedral E. ctahedral Square Planar 7. Determine the percent yield of a reaction that produces 28.65 g of Fe when 50.00 g of Fe23 react with excess Al according to the following reaction. (Molar masses: Fe = 55.85 g/mol, = 16.00 g/mol, Fe23 = 159.70 g/mol) A. 61.03 % B. 28.65 % C. 57.30 % D. 20.02 % E. 81.93 % Fe23(s) + 2 Al(s) Al23(s) + 2 Fe(s) 8. Which of the following statements is TRUE? A. A covalent bond is formed through the transfer of electrons from one atom to another. B. A pair of electrons involved in a covalent bond are sometimes referred to as "lone pairs." C. It is not possible for two atoms to share more than two electrons. D. Single bonds are shorter than double bonds. E. A covalent bond has a lower potential energy than the two separate atoms. 9. How many moles are in 25 mg of 2? (Molar mass = 16.00 g/mol) A. 7.8 10 4 B. 1.6 10 3 C. 0.40 D. 0.80 E. 800 4
10. Consider the reaction: 2 N(g) + 5 H2(g) 2 NH3(g) + 2 H2(g) A reaction mixture initially contains 5 moles of N and 10 moles of H2. Which set of amounts best represents the mixture after the reactants have reacted as completely as possible. A. 1 mol N, 0 mol H2, 4 mol NH3, 4 mol H2 B. 0 mol N, 0 mol H2, 4 mol NH3, 4 mol H2 C. 3 mol N, 5 mol H2, 2 mol NH3, 2 mol H2 D. 0 mol N, 1 mol H2, 5 mol NH3, 5 mol H2 E. 3 mol N, 0 mol H2, 4 mol NH3, 2 mol H2 11. What is the correct relationship between bond order, bond strength, and bond length? A. As bond order increases, bond strength increases and bond length increases B. As bond order increases, bond strength increases and bond length decreases C. As bond order increases, bond strength decreases and bond length increases D. As bond order increases, bond strength decreases and bond length decreases 12. Place the following in order of increasing A-Se-A bond angle, where A represents the outer atoms in each molecule. F Se F Se Se A. Se6 < SeF2 < Se2 B. SeF2 < Se2 < Se6 C. SeF2 < Se6 < Se2 D. Se2 < SeF2 < Se6 E. Se6 < Se2 < SeF2 13. Give the hybridization for the in 2, assume that is the central atom. A. sp B. sp2 C. sp3 D. sp3d E. sp3d2 5
14. Which compound has the highest carbon-carbon bond strength? A. CH3CH3 B. CH2CH2 C. HCCH D. all bond strengths are the same 15. Which of the following describes sp 2 hybridzation? A. Three orbitals are hybridized, one p-orbital remains unhybridized B. Three orbitals are hybridized, one s-orbital remains unhybridized C. Three orbitals are hybridized, no orbitals remain unhybridized D. Four orbitals are hybridized, no orbitals remain unhybridized E. Four orbitals are hybridized, one s-orbital remains unhybridized 16. Draw the Lewis structure for the molecule CH2CHCH3. How many sigma and pi bonds does it contain? A. 8 σ, 1 π B. 9 σ, 0 π C. 9 σ, 1 π D. 7 σ, 2 π E. 8 σ, 2 π 17. Which of the following describes the carbon in the best Lewis structure for HCN? A. Carbon has two double bonds B. Carbon has two single bonds and two lone pairs C. Carbon has a single bond and a triple bond D. Carbon has one single bond, one double bond, and one lone pair E. Carbon has one single bond and three lone pairs 18. Which of the following describes the molecular geometry and polarity for Xe3? A. Trigonal planar and non-polar B. Trigonal planar and polar C. Trigonal pyramidal and non-polar D. Trigonal pyramidal and polar E. T-shape and polar 6
19. Identify the compound with the highest percent ionic character. A. HF B. H C. IBr D. HI E. LiF 20. In the chemical reaction N2 + 3 Mg Mg3N2 if you begin with 1.35 moles of Mg, how many moles of N2 are required to react all of the Mg? A. 0.45 B. 1.01 C. 1.35 D. 1.80 E. 4.05 21. Consider the Lewis structure for formic acid (C2H2). Determine the hybridization of the carbon atom. Then determine the total number of sigma (σ) and pi (π) bonds in the molecule. A. Carbon hybridization= sp 3, 3 σ bonds; 2 π bonds B. Carbon hybridization= sp 3, 4 σ bonds; 1 π bond C. Carbon hybridization= sp 2, 4 σ bonds; 1 π bond D. Carbon hybridization= sp 2, 3 σ bonds; 1 π bond E. Carbon hybridization= sp 2, 3 σ bonds; 2 π bonds 22. How many of the following statements about molecular orbital theory are true: Bonding orbitals are lower energy than atomic orbitals Non-bonding orbitals arrive from destructive interference of atomic orbitals Molecular orbitals arrive from a linear combination of atomic orbitals Filling molecular orbitals follows Hund s rule A. none B. one C. two D. three E. four 7
23. For the following four bonds (1) Br Br, (2) C S, (3) C N, and (4) K F, which statement is true? A. Two of them are polar covalent bonds B. Two of them are pure (non-polar) covalent bonds C. There is no ionic bond. D. nly Br Br bond is pure (non-polar) covalent E. None of the above is true. Consider a molecule of P5. For questions 25-34, indicate whether each statement is true (A) or false (B) regarding P5. 24. The bond between P and is polar 25. P5 is phosphorus pentachloride 26. When the preferred Lewis structure is drawn, no lone pairs appear on P 27. has higher first ionization energy than P 28. Its electron configuration is 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 2 29. has a larger atomic radius than P 30. The molecule has sp 3 hybridization 31. P5 is a polar molecule 32. Its molecular geometry is trigonal bipyramidal 8