Key_EXAM_2 - CHEM 25 Em#2 08 NovemberZOflfi NAME E E1...

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Unformatted text preview: / CHEM. 25: Em #2 08. NovemberZOflfi NAME: E E1? PIea'Se check-the studioto which you are assigned: Monday PM Wednesday PM Thursday AM Tuesday AM Thursday PM Tuesday PM Friday PM This exam must be completed without the aid of books, notes or colleagues. You may use a noneprogrammable calculator; if your calculator is programmable, you must present it to a TA and have it cleared before you begin the exam. All answers must be clearly written in the. mace indicated and mathematical work must be shown for full credit to be awarded for numerical answers and for all answers for which calculations are carried out. Please write your name on the top of each page. A periodic chart is included as the last page of the exam, along with some equations and constants; Good luck .. . and remember: “He who knows nothing doubts nothing.” French proverb 'I make big batches and freeze it." s25» NAME: E E} [I] (15 points) No partial credit will be awarded on items (A) through (E); you must have each answer completely correct for 3 points to be awarded. (A) (3 points) Circle the letters of the designations in this list that are possible; if all-are possible, circle (f): .P @P (d) 3f .25 (f) allare possible (B) (3 points] The possible values of the orbital angular momentum quantum number ((3) of a 313' electron are: (a) +1t2,_-l/2 (b) -l, 0, +1 (c) 0, 1, 2 (d) 1, 2, 3.01m of these sets is possible (C) (3 points) Possible values of the magnetic quantum number, m; , of a 313 electron are: (a) 2 (b) 2, 1, 0,-1, —2 (c) l, 2, 3 .1, 0, +1 (e) none of these is possible- (D) (3 points) Circle the letter of the smallest acceptable value for the missing quantum number (n) inthis series: n= :822; m,=0; m5=+]/2 (a) 1 (b) 2 @3 ((1)4 (e) 5 (f) none of these is acceptable (E) (3 points) Circle the letter of each true statement in the following. Ifnone are true, circle (e); if all are true, circle (1): file existence of discrete, quantized energy levels in an atom may be inferred from a o - 'c line spectra. (1)) (An atomic orbital represents a fixed path followed by an electron around the nucleus of an atom. .‘he greater the frequency of electromagnetic radiation, the greater its energy. (d) The energy of electromagnetic radiation increases as its wavelength increaSeS. (e) None of these statements is true. (i) All of these statements are true. NAME: [2] ('34 total points) [A] (12 points) The total mass that a balloon can lift is given by the difference between the massoftheair displaced by the balloon and the mass of the gas inside the balloon. You are part of a team at NASA that sends a small hot air balloon to Mars on a Marti-an rover. Your Martian rover can inflate the balloon with helium heated to a temperature of 40°C. The temperature on Mars the day you: balloon is scheduled to be released is a balmy —35"C, and the amaosphen'c pressure is: 7.35 torr. (Yes - the value is 7.35 torr; the pressure on Mars is about 1/100 of the pressure on Earth.) The air on Mars (mostly CO; and N2) has an average molar mass of 43.2 g‘fmol. When filled with helium, your balloon has a radius of 2-5 .0 cm. The balloon is designed to lift 'a small probe and carry it away front the InVer. The mieroprobe has a mass of 1.1250 9,. What is the total mass your balloon can lift under these conditions? Does your mission have -a chance of success (Le. can the balloon lift the microprobe), or should you delay? (HINT. consider your balloon a sphere; the volume of a sphere' 13 V: (4f3)7::t3 and 1 L=1000 c1113; the pressure in the balloon rs the same as the atmospheric pressure.) Answer: mass in g that the balloon can lifl Circle one: .looray! The mission has a chance (b) Better postpone and wait for a colder day on Mars Work space: fitne- (E; ): Mt mm:)=f&(o.oszou;gfi_n)(3tek) Iowan? 4%: Kmn’c *sz = 0 anti-'7’? =70 09863. {In m“- (f 33"; --7;. (as. hauls) , 1:3— (0.08206 Lat-6» )(zegk) #0100047"? 5‘3 2% Hm: I: mg -l 900:3, /. 90,03 3 /.30I9:-7I.503 qu/ NAME: EEZ [B] (22 points) We’re still on Mars with the rover. The rover has been equipped with little rover-sized airbags to protect it when it falls through the Martian atmosphere. They deploy when the rover slams into the ground. As a NASA scientist, you have developed a Special way to package liquid nitroglycerine so that it explodes when the rover crash—lands entire surface of Mars. Its explosion produces gases that inflate the airbags. Here is the balanced equation for the explosion of nitroglycerinc: CHg-ONOZ 1 4 mom: (1) is 6N2(g)- + 12 C02(g) + 02(8) +10 Hz-Ols) l CH2—0N01 (i) (4 points) Under the conditions on Mars, if this reaction produces 1.0 L of oxygen gas, what is total number of liters of gas produced when the liquid explodes? Answer: total number ofliters ofgas ‘ 2? L. Workspace: /.0 L 07, * Io Lil-LO ’3— L 507/ 6 L N1, 2"] L 90.4.; (ii) .(8_ points) Now we’re back on Earth NASA captures an experimental Russian land rover that used different technology to inflate the air bags. You collect a sample of the gas from. the Russian rover’s airbags and find that, here on Earth, when the temperature is 18°C and the pressure is 745 ton, a quantity of the gas weighing 03079 g compiles a volume of 250.0 mL. You suspect that the gas is one on the list below. Circle- all peasible choices from the list that could possibly be the unknown gas. (Allow for +[- 3% error in your determination.) (a) 6.02 (b) PH; (c) NH3.=H2_0 [email protected] (gm I-‘r' 30 30 w 3 u so #0 3/mu/1 Workspace: 13.155" ”4," 0.2504. c .304??(o.03206_1-1_7"_Iz 2m:- flofw) ( ) X Km" X ) X = 30.0? male, 4 / *(7/ NAME: 'C E ’ (iii) (10 points) You also expefimont with different combustion reactions of non- carbon. fuels to power the rover. You are considering using the combustion of hydrazine (N2H4,(I)) as a potential energy 3011103: N111: .(1) + 02(g) 9 N2(g) + 2H200) Calculate the heat of combusfion of one mole of hydrazine in H from the following known reactions: 1mg) + 4 H200) -) N2H4(l) + 2 H202 (I) +8182 k1 H2(g) + 02(g) 9 H202 (I) 487.8 k] H2(g)' + U2 02(g) -) H200) -285.3 kJ Answer: 9622-2 It. . NZHY(1)*%ET 2‘1) +fl“ 10(1) “$532” ,, i. wofloiwuchm, zC-IW-m) LW) "W‘jfiflfl if) 1623mm) Work Space: [Val-11%!) '4' 02(3) —? 2%3)+ZHL *éZleJ [3] ( 22 total points) Now you‘re in the Marvel Comics Universe, where the character of Wolverine is unique because his skeleton is covered by a mysterious metal alloy called adamantine. In the Marvel universe, you take ajcib with a man called as Magneto, who wants you to characterize one of Wolverine-’5 adamantine claws that he has acquired. You run the following experiments: [A] (10 points) You have. apiece of adamantine that weighs 26.92 g. You heat it to 100°C by dropping it in boiling water. You then take it out of the boiling water and put it in a well insulated beaker that contains 175 g of Water at 166°C. The temperature of the water in the beaker rises to 23 9°C. What is the specific heat of adamanfine in JIg°C? (NOTE: the specific heat of water is 4.184 J/gDC') Answer: specific heat of adamantine "‘ #6 I I .C Work space: - r—-"-——\ _ [(2e.?23)(¢:m)[(239rwarez): (n53)(tf.raégz)(zsfi—m.e)2 , 5554.: = _ .37 _T Put" zoygat 2'6“} 2'“?TC [B] (6 points) Magneto then has the idea that he’s going to overpower Wolverine by generating an electric current in his body by shining light from a laser on the .adamantine. You determine that the work mam (o) of adamantine is 2.37- x '1 0-131. The most powerful laser Magneto has operates at a wavelength of 2-12 mm (1 nm-= 1x109 In). Doeathis laser have sufficient energy to expel electrons from the surface of :adarnantine? (Mathematical Work must be shown clearly for any credit to be awarded for your ans'Wer; clearly show the comparison on which your answer is based.) Circle one: yes o Comparison: Elam 4 £44.. Worktojusfifwswev g: fly = fig 46.5916 53193.00 ”0"”(5) A. (71.2: (0‘5") = 9. 58'): 10"11 6 NAME: E5 1 [C] ( 6 points) Answer only one of the following: If your answer to question [B] on the previous page is ‘yes,’ what is the kinetic energy of the expelled elecimns? Answer: ICE of electron If your answer to question [B] is. ‘no,’ what is the minimum wavelength of light in mm needed to expel electrons from the surface of adamantine? Answer: minimum A. 6? 3 n r7»... i of light Work space: _ s- ' F=§= L‘HHO ’J = fig : (c.63vros5s)(z.oovo:a) A xx A: 5,?3no’i’ 567.3nm NAM: KE- [4] ('9 total points) You get a job in a drug testing laboratory that is evaluating the impact of a new pharmaceutical 0n human metabolism. You need to trap the C02 given off in a subject’s exhaled breath over a period of several minutes. You remember how a scrubber works on a huge smokestack to: remove oxides of sulfii'r from exhaust gases, and you design 'a small device that Works on the same prineip'le. thr device takes exhaled breath and bubbles it through an aqueous suspension of lithium oxide. A precipitate forms when You do this. Your boss asks you to. present your design to the patients in the study and explain to them how it works chemically. Write three balanced molecular equations that describe what happens (1) when CO; gas is bubbled through water, (2) when solid lithium oxide is suspended inwater; and (3) when the products of reactions (1) and (2) react. Work space: NAME: ICE", [5] (20 total points) Methyl ethyl ketone (known as MEK; C4330: mol. wt. 72.10 g) is a- liquid solvent used in the manufactm'ing of smokeless powder. Determine how much heat is assooiated with the complete combustion of methyl ethyl ketone using a calorimeter like the one you used in the lab to determine the heat content of fuels. You bum MEK to heat 200.0 g of water in the calorimeter. Here is your data set: mass of MEK burned: 1.087 g heat capacity of calorimeter: 0.643 kJ/°C specific heat of water: 4.184 J/g°C AT for water and calorimeter: 210°C (a) (10 points) Calculate the heat of combustion in kl of one mole of MEK. Answor: heat of k J W k- --: 1') ti _. or space com us on 214,50 /rml¢ = . ELJO h ' fan (0 we fcl(zs.o°c) +(wits/floaaamoaxzeo c) .-. root M + 20.?2 N = wok-J yea-Io NEIL :2“, . ' - _. {-0343 ImhMEt— ~3w sat =z¥5olc3 (b) (10 points) Someone in your laboratory runs the same experiment in the same r717] calorimeter, but replaces the water with 200.0 g of the liquid carbon tetrachloride (CCLQ. This time,_ it only requires 0.5318 g of MEK to be burned to raise the temperature 250°C. Whatis the specific boat of CC14 in J/g°C?' Mass of MEK burned: 0.5318 g Heat capacity of calorimeter: 0.643 kJEC'C Specific heat of CCh: C?) AT: 250°C Answer: specific heat 0. 3?3 J I a of CC14 C Workspace: 0.53:3 Mex 2-.“wa = *18’.0¥kJ 3 Tz-loa/mak. 3w». )(mog )aso'c) [000 + {$20453 'r' [6-0 ?LJ 4' ($.M.)(200.03)(ZS.075) . 9 [000 . . SF-htqv = 0.393341; 4 3m s. Hm; u e mews 1:.Té)£zs.o°c)+( ...
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