CHM2210SampleExamAnswers - NAME W STUDENT Scamp/e 624...

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Unformatted text preview: NAME: W STUDENT #: Scamp/e 624% FLORIDA INTERNATIONAL UNIVERSITY DEPARTMENT OF CHEMISTRY Dr. Keller EXAM I CHM 2210 Spring 2000 Be clear and neat; a poorly-drawn structure may be misinterpreted. To obtain partial credit, you must Show your work. I. LEWIS STRUCTURES — Supply Lewis structures for each of the following. Be sure to include formal charges and unshared electron pairs where appropriate: (-9 1. [CH2NH2]® 1/..(1, 2%.4 [3 points] H H 2. Draw two different Lewis structures (resonance structures) for the molecule N20. The arrangement of the atoms is given beiow: [4 points] II. DRAW A SECOND RESONANCE STRUCTURE for each of the following compounds as shown by the curved arrows. {2 points each] HI. 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] CHM 2210 Spring 2000 Exam 1, Page 2 For example, 2. Name the orbital that holds the unshared electron pair in each of the following compounds: a. :NI-IZCH3 5P3 . b. H—CzN: [2 points each] 5? IV. PHYSICAL PROPERITES 1. EXPLAIN why NF3 is less polar than NH3 by following the steps below. 3. Draw a Lewis structure for each of these molecules. [3 points] flail-1%: Hwy—+4 2?: H 5'4 b. Draw a Selma] picture which shows 3‘ of each of these molecules. [3 points] ..M ~ my @‘r M s“ c. Show the individual bond dipoles in both molecules on your three dimensional structures (above). HINT: Remember that if an atom has a lone pair, there is a dipole pointing from the atom toward th lone pair[ X : ]. [3 points] (I. Based on your drawings in Parts b and c, EXPLAIN (briefly) the observed difference in the ese two Anolecules. [3 points] £35???“ N L alum m drank almemw MA nth/l 2mm 0va vs Mia bum! MU m fame 7 chad-mt OM49» infiflm M +11%: CHM 2210 Spring 2000 Exam I, Page 3 2. Circle the compound in each of the following pairs that would have the higher boiling point: [1 point each] "HAL ”'"F b. H; 0,. V. 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 C1H14Q. [3 points] b. Draw a secondary amine with the formula CSHHN. N /\' [3 points] it c. Draw any carboxylic acid containing a phenyl group. [3 points] i :o'. \l . . 2. Identify and label the four functional groups in the molecule aspartame (the artificial sweetener in Equal). [5 points] /© 0 0 $3" / \ H CHM 2210 Spring 2000 Exam 1, Page 4 VI. ACIDS AND BASES 1. Draw the conjugate acid of each of the following bases: [2 points each] . O" o?” 9 ‘ ‘H \H b. H—C-.__-——C A—CEGQ 2. Draw the conjugate base of each of the following acids: {2 points each] :0 2 CH a1 ‘ b [—16 'é '0' '9 a. ‘ . —— — . 3"2 uhwgll --_n.-- l t O 0 . 9 II ‘ \ :Q :0 —tS‘—* Q a. .’ H )0 l o 0 0 [email protected] o 3. Consider the 0/ A0 @ following acids: A B c D pKa = 2,0 9 10 5 a. Which acids are strong enough to react almost completely with NaOH? [the pKa of H20 = 15.7] [3 points] 3&9 b. Nae‘3 HCO3 9 (sodium bicarbonate) is the conjugate base of H2C03 (carbonic acid) [pKa = 7 .8]. Which acids will react completely with Nae HC03 9 ? [2 points] D 4. Given the following acid/base reaction: A useqagoezwtwwf.’ . . CHM 2210 Spring 2000 Exam 1, Page 5 "' "' C H + '(?:H C +— C4 W 2m ' 3 f (ll/Lidia wait/tux, a. mplete the equation. [3 points] . ,.v¢W3;W‘V¥4-"Ifl‘iww mug»; “7(qu , ;«m;$§g€g§m§flw;¢. b. Show the conjugate acid/base pars in the space below. / [4 points] QAJMHL/CllgNli cit/f c349 0M (”ML Owl km, c. The pKa of CH3NH2 is 28 and the Ka of the conjugate acid of : CH3‘3 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 equilibrium (does it favor the left side or the right side?) [2 points] MM VII. CONFORMATIONAL ANALYSIS . 1. Using the templates below, draw the two chair conformations of cis-l-ethyl-3~methylcyclohexane, and circle the more stable conformation. [5 points] Nzfl 2. Using the templates below, draw the two chair conformations of trans-1-ethyl-3—methylcyclohexane, and circle the more stable conformation. [5 points] haze—a ...
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