EXAM12009KEY

EXAM12009KEY - CHEMISTRY 2261 EXAM 1 September 16, 2009...

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Unformatted text preview: CHEMISTRY 2261 EXAM 1 September 16, 2009 LIST number NAME (PRINT)____________________________________________ 1 2 3 4 5 6 A NSWER 7 8 9 10 K E 11 12 13 14 15 16 Y TOTAL 1. (10 pts) Fill in the missing elements in their proper positions in the Periodic Table: 2. (7 pts) Add formal charges to the following Lewis structures where necessary. 3. (10 pts) Draw acceptable Lewis structures of the following neutral compounds by adding all the nonbonding electrons, multiple bonds and any necessary formal charges. 4. (4 pts) Calculate the equilibrium constant (Keq) for the following acid-base reaction. 5. (6 pts) Fill in boxes on the right (using s, p, sp, sp2, or sp3) to indicate relative energies of the 5 indicated orbitals. Note that there are seven boxes and only five orbitals, so two of the boxes will be left empty. 6. (8 pts) For the molecule shown below, identify the hybridization (sp, sp2, or sp3) for each of the labeled atoms. c O a C d e N OH + O – O g h N b H a sp2 b e sp2 f sp sp3 f O c sp2 d sp2 g sp2 h sp3 7. (4 pts) Rank the following group of compounds in order of decreasing acidity. H NH2 strongest acid H Cl H H SH H Cl H SH H PH2 PH2 decreasing acidity 2 H NH2 weakest acid 8. (6 pts) For the following group of anions: • provide the hybridization of the indicated carbon atom • rank in order of increasing base strength. 9. (8 pts, 4 pts ea) For each acid-base reaction: ! Indicate whether Keq is greater than or less than 1 (>1 or <1) ! Indicate the effect responsible for the difference in acidity (electronegativity, size, inductive, resonance, or hybridization) which influences the equilibrium constant. 3 10. (6 pts, 3 pts ea) basic form a) Determine the pH at which 99% of CH3CH2SH (pKa = 7.9) will be in a form that possesses a charge. pH = pKa + log(99/1) ! 7.9 + 2 = 9.9 basic form b) Determine the pH at which 9% of CH3CH2SH (pKa = 7.9) will be in a form that possesses a charge. pH = pKa + log(9/91) ! 7.9 – 1 = 6.9 11. (4 pts) Rank the following compounds in order of increasing boiling point. 12. (5 pts) Give the product of the following reaction (as a properly drawn Lewis structure): Cl BeCl2 + Lewis acid H H3C N CH3 – Cl Be + N H HC CH H H C H H H CH3 Lewis base 13. (4 pts) Draw a Lewis structure for each molecule below. Indicate (circle) which molecules (if any) will have a molecular dipole. (Hint: consider the hybridization of the central atom). 4 14. (8 pts) Draw structures corresponding to the following IUPAC names: 15. (4 pts, 2 pts ea) Answer the following questions about the pair of Newman projections drawn below representing two staggered conformations of an alkane. a) Identify (circle) the lowest energy conformation. b) Provide a skeletal structure and IUPAC name for the alkane represented by this pair of Newman projections. 2-methylbutane 16. (6 pts) Add the six remaining C-H bonds to the chair cyclohexane drawing provided below. 5 ...
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This note was uploaded on 06/09/2011 for the course CHEM 2261 taught by Professor Crowe during the Spring '08 term at LSU.

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