CHM2210SampleExam - u. NAME: STUDENT #: FLORIDA'INTE'...

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Unformatted text preview: u. NAME: STUDENT #: FLORIDA'INTE' RNATIONAJJ'UNIVE’ DEPARTMENT OF CHEMISTRY ‘ ' Dr. Keller CHM 2210: Spring 2000 Be clear and neat; a poorly-drawn structure may be To obtain partial credit, you must show your work. , - . ’ a 1 r- . I. LEWIS STRUCTURES — Supply Lewis structures for each of the following. Be sure to include formal charges and unshared electron pairs where appropriate: ‘ _ aria; , ,24',‘ ' r, angry-er jumper-3’s. . 1. [CH2NH2]$ , [3 points] 2. Draw two different Lewis structures (resonance structures) for the molecule N20. The arrangement of the atoms is given below: [4 points] 11.. DRAW A SECOND RESONANCE STRUCTURE for each of the following compounds as showr by the curved arrows. [2 points each] (9 m a. CH3_ C|:— CH3 <——> b. H—b—s o <——> '3 Q CHM 2210 Spring 2000 Exam 1, Page 2 III. ORBITALS: 1. In the same manner as shown in the example below, label each bond in the alkyne X with the names of the orbitals that are overlapping to form them. [5 points] For example, E /C— E C— H H X 2. Name the orbital that holds the unshared electron pair in each of the following compounds: I a. :NHZCH3 b. H———CEN: [2 points each] IV. PHYSICAL PROPERITES 1. EXPLAIN why NF3 is less polar than NH3 by following the steps below. a. Draw a Lewis structure for each of these molecules. [3 points] b. Draw a 3-dimensional picture which shows the shape of each of these molecules. [3 points: CHM 2210 Spring 2000 Exam 1, Page 3 V. c. Show the individual bond dipoles in both molecules on your three dimensional structure: HINT: Remember that if an atom has a lone pair, there is a dipole pointing from the ator the lone pair [ ;>] . [3 points] d. Based on your drawings in Parts b and c, EXPLAIN (briefly) the observed difference in the polarities of these two molecules. [3 points] 2. Circle the compound in each of the following pairs that would have the higher boiling point: [1 point each] N/H a. (:1 or C ___CH3 C. % or O F F F b. H or H F FUNCTIONAL GROUPS 1a. Draw a five-membered ring cyclic ether (i.e., oxygen is one of the atoms in the ring) for a compound with the molecular formula C7H14O. [3 points] b. Draw a secondary amine with the formula C5H13N. [3 points] c. Draw any carboxylic acid containing a phenyl group. [3 points] CHM 2210 Spring 2000 Exam I, Page 4 2. Identify and label the four functional groups in the molecule aspartame (the artificial sweeter in Equal). [5 points] \2/C\ / \ OCH3 Aspartame VI. ACIDS AND BASES 1. Draw the conjugate acid of each of the following bases: [2 points ea< .. ' e 3- CNxH b. H—CECZ 2. Draw the conjugate base of each of the following acids: [2 points eat 10 I (9 . . || . . E) a. CH3Q_H2 b. HO—S--—O I CHM 2210 Spring 2000 Exam 1, Page 5 o 0 0 o@ o' 3. Consider the G A 0 following acids: A B c pKa = 20 9 10 5 a. Which acids are strong enough to react almost completely with NaOH? [the pKa of H20 = 15.7] [3 points] b. Nae“) HC03 9 (sodium bicarbonate) is the conjugate base of H2C03 (carbonic acid) [pKa = 7.8]. Which acids will react completely with NaEB HCO3 e ? [2 points] 4. Given the following acid/base reaction: 6 CH3NH2 + ICH3 _‘ a. Complete the equation. [3 points] b. Show the conjugate acid/base pairs in the space below. [4 points] c. The pKa of CH3NH2 is 28 and the Ka of the conjugate acid of :CH3e is 1x10'40. (1) Label the stronger acid, the stronger base, the weaker acid, and the weaker base. [2 points] (2) Indicate the direction of the equilibrium (does it favor the lefi side or the right 3 [2 points] ...
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CHM2210SampleExam - u. NAME: STUDENT #: FLORIDA'INTE'...

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