142exam_answers_Final_Exam_key

142exam_answers_Final_Exam_key - K: 7&9 CHEMISTRY...

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Unformatted text preview: K: 7&9 CHEMISTRY 120A FINAL EXAMINATION (Version 3) Autumn 2007 Tuesday, Dec 11, 2007 Name: TA Section: Student Number: TA Name: Score (pg) 1 2 : GOOD LUCK! Watch the sig figs, and units 3 4 SHOW YOUR WORK! 5 l 6 l 7 l Total (x/100) . I. DEFINITIONS . Define any eight (8) of the following 12 terms in the context of this course (2 points each) ‘2 . *electronegativity {fir re/o/g'w 911%! :f 9» .24“ I”) 9 Amy )4 V 4/4qc/ handy r/ecfl’em- E i l *Pure substance ‘? ’lj/v of 4,914” affixed CW/ar”{a\ /r/e»¢.,/ * av Covfih’v”), W7! Jr/avr 44v {/4 lcg/ Ma: rad/19.;th mar/P ‘I 7“? a)? 470;;- «eff r4»: ewe/o»)? {W I . “1'4 / y I *formula unit 7/4,.” ,flgrfiffif’g‘j? "hurrah/g g/wa :‘am'c «yum/E E. l * polyatomic ion *dipole-dipole force signal-9A 59/“;vAZF/"xzé CJ‘GV W” at a, m Pa. 1' *heatoffusion be?! P m// {9 clog 94434))” _ mat porn/7C _ * eqUIValent (EQ) / m/p g/fayl'Kw/yvr flaaé/bnj/c/arya/ fa»: _ *solubility mqn'bogm quay”?! .fxv/wé “A?! an» 043:9/4- "h Ava) xe/wnf ,/ c, 313-0»; Aviva/4.». *Le Chatelier’s Principle M", 9 594,9,- ,’3 ,f/MA q= * I,” (94’7/5 ra‘tuu , fl: 6272 Z’I'ty’h :J/fi >4 int/iv»! .pressure or Mac, Alisha, 74’"? emé/ J) 79;- mv/ecw/q I'M 44/43/514: wl’é #4 ova/é of: #f egg-A,be ll. CONCEPTUAL, SHORT ANSWER ( subtotal = 96 pts, each as indicated) 1. Give the strongest attractive force or bonding type for each of the following: (a) between H and CI atoms within a molecule ofo’l—SI fa/qv cam: éu/ 4"") (b) between HF molecules in liquid HF ll—é to} (0) between N and N atoms within a molecule of N2 men-19’4" 5°W/6‘71/“7/ (d) between Ne atoms in liquid Ne askpelxz‘ah ' (e) between Na+ and l‘ ions in a crystal of Nal lml'c (f) between CH3l molecules in liquid CH3I dipole ~a’I' e 2. For each of the following species: (a) Draw the electron dot structure, (b) Name the VSEPR configuration, and (c) Name the molecular shape 3er H28e NH4+ BF3 . .. . - ,3: + _; ‘fo'é’caf- - y’gfy n: I'm-1;] 3: , g. ’5'. - y VSEPR 0'” 96’ klflfile‘c/R/ Me‘dw/ Mm» Mol shape Ova-r ban/L #ezlslea/m/ dry-"J ,o/omv 3. Draw two resonance structures for nitrous oxide N20. (The central atom is N) [157: N:g‘_>’] c——> [ :Ns/v-g': 4. ln heating a system of water and steam at the boiling point, why does the temperature remain constant until 'all the water has evaporated? q/l gar; )0); )C'l'74 W4” ya “’4‘; Cam»?! Mym 9// 1?? 23' day/4‘5), 5. Name the following compounds: FeCl3 CuzO N203 P205 in»: my) cl/on‘o/f (op/n (z) cow’ng arbeer ow?” *I'G‘XI'JC 6. Write chemical formulas for the following compounds: sodium sulfate magnesium bicarbonatt Iv?u Say I”; {yC05)L / s’ZBZfi‘ZJ 23/ ‘43’ 30’ ’09}: ’ of r, 7. Write electron configurations for the following atoms: Ga Zn. . . r] 952 hwy/0’ , . 8. For each of the following types of radioactive decay, indicate the change in the mass and the change in the charge of the decaying nucleus: Decay type Amass(amu) A charge beta 0 +1 alpha -2 - Z positron Q ~/ gamma Q Q 9. Theradioactivity of 14C i‘rrthe charcoal of an ancient campfire has decayed greatly. After 3 half-lives, whatfraction of its original radioactivity remains? If the half—life of 14C is 6 x103 yrs, how long ago was that campfire? Mang - ; X/cx/g’) ; Woo-9»; of ZX/oygv: 10. Give the maximum number of electrons which can be accommodated in each of the following: a single 3-d orbital the 4-f sublevel the n= 4 level _ _ _ z z: 2(7) #7 z {9/ ;32 11. In the following redox reaction, indicate which reactantspec‘ies is undergoing reduction and which is undergoing oxidation. Balance the reaction. LC3H8 + £0? ‘9‘ 3.002 + LHzo 7 7 0"a/k) redhred 12. In a mixture of air gases (N2, 02, 002), (CD/F) (a) each gas component has the same temperature , . _@/F) (b) each component gas has the same average kinetic energy CUF) (0) each component gas occupies the same volume (TE) (d) molecules of all gases move at the same speed @F) (e) this mixture can only be condensed to a liquid because of attractive dispersion forces between the gas molecules. 13. Potassium chloride KCl has a solubility of 34.0 g per 100. g at 20 °C. If 100. g of KCI are mixed with 200. g of water at 20 °C, What mass of KCI will NOT dissolve? V . ‘ rd. : (£92 “'2? -; ' 63.; dine/W 2‘» 200} 119, v /00.—' 63,—” 32,} «3333" wire/w 14. A solution contains 40 'mEq/l of Cl- and 20 mEq/l of HPO4 2-. lf Na+ is the + only cation, what is the concentration of Na in mEq/L and in M? 90 +20 = Comm?) o/mcj or ’06: c4996 .3 . [NJ]: 604.57 = com 241 15. Consider the chemical equilibrium: 3 02 (g) + heat 9 2 03 (9) For each of the following changes, indicate whether the reaction shifts toward products (—)), toward reactants (6-), or does not shift: 1 (a) adding more 02 6- (b) adding more 03 <——- (c) lowering the temperature —§ (d) increasing the pressure meme) adding a catalyst 16. Write the equilibrium constant Kc for the following equilibrium reactions: _ {Maj “ kc~ 0,922.0; (b) 082(9) 9? 4 H2 ('9) <----l>' 0144(9) +2 strg) mm ___,L_ ,[02] (3) 2M9 (3) + 02(9) <----> 2M90(S) Kc: Ill. QUANTITATIVE ( 15 pts each, subtotal = 90 pts) 1. How many milliliters of2.00 M Pb(N03)2 will react with 50.0 mL of 1.5 M KCl? Pb(NO3)2(aq) + 2 KCl (aq) ->PbClé(s) ' -+ 2 KNO3 (aq) 1 L 1.50 moles KC] = x ~——~———— = 0.0750 mole KCl /&‘59/b. 50.030: x 10mm, 0.050015 IE ' 1 W 1 L solution _ . X ————————- X -——~———————- — 0.0188 L solut10n 0.0750meieKCI 2 2.00 3 2 0.0188 15 x 1000 mL = 18.8 mL solution 2. ‘The equilibrium constant Kc = 54 at 425 °C for the following chemical equilibrium: H2 (9) + l2 (9) 9 2H| (g) If the equilibrium mixture contains 0.030 M of Hi and 0.015 M of l2, what is the equilibrium concentration of H2 ? [HI]2 [H2102] ' Rearrange KC to solve for [H2] and substitute concentrations to calculate [H2]. 9.23 KB = [HI]2 _ [0.030]2 _____________ 2 —3 K002] _ [54][0.015] 1‘1 X 10 M [H2] = x i l r l l l i l l r r i r l l l L a g. l iv 3 l l x l l i l s 3. Consider the following reaction of heating calcium carbonate (limestone) to make calcium oxide, an essential ingredient of concrete: CaC03(s) + heat <———-> CaO(s) + 002 (9) Write the equilibrium constant for this reaction Kc If 2.00 moles of Ca003 react, how many liters of 002 are produced at STP? (7.797 The mole—mole conversion factor is obtained from the reaction and used to convert to moles of gas, and the STP molar volume conversion factor is used to convert moles of gas into liters of gas, as shown below: hmmfififi 224L ZDOmdafihfifi‘X————~—~——X——————— 3 lmdeefiifi lnmbfrg =44.8Lco2 4. Aluminum oxide is formed from its elements by the reaction: 4 Al (5) + 3 02 (g) —) 2 Al203 (5) What mass (grams) of AI will react with 12.0 L of 02 at'STP? im%fifi 4maxm mbgm 750 120L6’X-—~———-X x—————— l 2 2 224L€5 SmQafiZ lnwb¢fl =193gA1 5. Calculate the amount of heat energy (in calories) required to warm 55 mL of water (density = 1.00 g/mL) from 10. °C to 100. 0C, and then vaporize it all to steam at 100. °c. (Note: the specific heat of liquid water is 1.00 cal/(g OC, and the heat of vaporization of water is AHvap= 540. cal/g) (Q {/3 d.)1"wo calculations are needed: . 1.0g 1.00% lkcal X—————X X90°€X =5.0kl 55M 1 er ggc “mow ca 1.0g 540w lkcal SSWX —————— X X = 30. kcal 1 mlrwatéf 1 g 1000M . Total: 5.0 kcal + 30 kcal = 35 kcal V =35ooo cal A5 “CL 38th 6. In the following reaction, the amount of each of the reactants is 20.0 g. 3 N02 (9) + H20 (l) 9 2 HN03 (aq) + NO (9) Calculate the HN03 produced (in moles), and indicate the limiting reactant. 1 mele’N‘O'z‘ 2 moles HNO; . . . >< —-—-—- X ——————‘ 0.290mole HNO smallest) [5‘62 b)200g»N0§ 46.0 2 3 2 :1 3( 200 . X ImGlC'HEU X 2molcs HN03 ' £sz 18.0g»H§C 1W = 2.22 moles HNO3 ...
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142exam_answers_Final_Exam_key - K: 7&amp;amp;9 CHEMISTRY...

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