Problem Set Solutions 1 - Chem 208 Spring 2008 Problem Set...

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Unformatted text preview: Chem 208, Spring 2008 Problem Set 1 Due Friday, Feb. 1 at 2:00 PM Name: SOL UT: 0 Ix.) 3 Lab TA: Lab Day/Time: 1. Antoine Laurent Lavoisier (1743-1?94) collaborated with the French mathematician Pierre Simon de Laplace (”49-18270 on problems in reSpiration chemistry. Their experiments with guinea pigs in 1780 first quantified the oxygen consumed (and carbon dioxide produced) by metabolism. They showed that respiration, in the lungs was similar to the combustion of coal: both processes produce C02 and release heat. Lavoisier and Laplace developed the ice calorimeter to measure heat released by animals during respiration or heat released during combustion. A nested chamber 6 was first packed with ice, T = 0°C. A combustible sample was then placed in basket f located near the ice. The entire device was thermally insulated by a double wall jacket a, to ensure that no heat was transferred to the surroundings. The sample was ignited, and the liquid water resulting from the melting of the ice due to the heat released by the reaction drained into a pan p through a stopcock. Old laboratory records, some of which are housed in the Cornell Library‘s Lavoisier Collection, document the experiments. Combustion of 1 oz of carbon melted 6 lb, 2 oz of ice. It is known that 601 Id of heat is absorbed when one mole of ice is melted at 0°C. Using this value, calculate the heat released for the combustion of carbon in Joules per gram and in klr’mol. Compare your calculated result to the modern value of 393.5 kJr'mol. Note that 1 1b = 16 oz. = 453.6 g Grams or"? ice melieci:(9(453.é,)+i(L{-§3.L) ‘—'- E7783“ Moles ‘ICemgHeolacl-nfij) l‘ROIIS/ err? =- ISL+-3 Mules- Mass 05; Catriona iOuf/leol : Tl; (LB—BL?) =28.‘{5_ Hedi— ab‘sorbe‘J : ng’xg molES‘ ice) (é.oi kT/mrQB +0 wit}— ; 327-% k3- : ice. cl/lce, + Cicadas». ; _ - 61.273 in? (fledged ClCatfbofl= ‘ ' I Chem 208, Spring 2008 Problem Set 1 Due Friday, Feb. 1 at 2:00 PM 2. An oxyacetylene torch is based on the combustion of acetylene in pure oxygen. The complete combustion of one mole of acetylene releases 1255 kJ ofheat. a) Write the balanced chemical equation for the complete combustion of one mole of acetylene gas in oxygen. :2: C2 H16; 2, Oates—3 2 Cog; ”2.08) b) Assume that all the heat generated by this reaction is used to raise the temperature of the carbon dioxide and water produced in the flame. What is the theoretical maximum temperature of the flame of an oxyacetylene torch? At constant pressure, the molar heat capacities of carbon dioxide gas and water vapor are 37.1 J/“C mol and 33.6 JF’C mol, respectively. Assume an initial temperature of 20 OC. Ldlrxen l male 0%: CLHL TS lawn—glad; Ljfluo PKDCLJCQ 2 moles 0? Col—K3} Cu“ mas-e. L 6} C ‘ I ll’ie ”balm/Q hefij— Capac'rljcol ‘H—‘fiefr‘fldd‘s 13' __, {1 Zmoles COL ”-‘ 37 '%I ‘k’ |mol€ ”3'0 k ”Cruel a“ mo flTfiL Ana/”fl Max:201 ,cla /ZSSkT:/Zs‘5‘x/0J Cigars: C3a5&[3a5 lZSSklogf—l 0C ijqs: 3—7—3 F” E IEHZ‘ CfiqJ‘ ,._— ' . =10rllc‘tllllééz ”$00013? Why mighth result be in error? 0) How does your theoretical result compare to the measured temperature of {abfim 0 Our“ CalCulA‘lQJ "Lamp was HIQQDZ, C. m WQSurP-‘cb lamp was C330“: 6 5; ”r a ”C. = t. BOOF"3Z F)? WSUIUJ o 2 3%” C l l 143 We. aSSuzwecl Hal/moi [Mg m our Calm/la M “m” ; W15 0‘ k”? W ’09.? ”From ‘Flawfi. Alfalforv-Q- i on "l-‘WI +0 l; 'l' Chadd/Lo. Con/slaujfion €344??? Sno'lC: mm Complgfitj Chem 208, Spring 2008 Problem Set 1 Due Friday, Feb. 1 at 2:00 PM 3 A 20. 0 gram chunk of an unknown metal at 200°C is added to 75. 0 grams water at 22. 0°C in a styrofoam cup. The final temperature is 26. 4°C. Neglecting the heat absorbed by the cup, determine the Specific heat capacity of the metal. Using the law of Dulong and Petit, which states that the molar heat capacity of a metal 15 about 6 cal mol‘] K'l, estimate the atomic mass of the unknown metal. Identify the metal COAS‘EI’Ua. 'I'HJA a"? Cdcrfi‘a.‘ 0’ mg,“ + fiwh‘t‘r :— O 9”“;le 7' __ Tame-3°11!" .. .? Mo! K 1:8— I mOlAr mass is 100 S/mol) SID 2.5.! .3— mgl ‘C - O-ZS lT/‘j‘c a —. , [1009/ a: Wergfip—a Molar mass 0? nah} '4 M: - egaorg/ml Merl-aft; Co 0329? 4. You buy coffee (200. 0 m1) served 1n a styrofoam cup3 %u/ agoc up late working 1n a chemistry lab, and want to drink the coffee right away, but at 95. 0°C, it is too hot to drink. You decide that the fastest way to cool the coffee is by dropping 40. 0 grams of dry ice, C02 (5), initially at -78 0°C, into the coffee. Note that C02 does not exist as a liquid at 1 atm; the solid sublimes directly to a gas. At «78 0 °C, 8. ”1'6 k] of heat IS absorbed upon sublimation of one mole of dry' ice. Assume that the final temperature of the C02(g) is the same as that of the coffee. You can neglect all heat losses and the solubility of C02 in coffee. Assume that the specific heat capacity of coffee is the same as that for water. The specific heat capacity, S = 0.850 Jfg°C for C02(g). indm'kmicfih¢5= (? Ce1)(stasF ?) 2s.r375.rc_ a) Calculate the quantity of heat (qsub) required to sublime 40.0 grams of dry ice to form gaseous C02 at -78.0°C. moles C02! -::_ L+O.O 9 : O.°10Cl LlL'l-O 34nd Clark 2 (0.90‘lmotes) (87L k37mole)—- 7 :ltlésk 79coir b) Write an expression for the quantity of heat (qgas) required to increase the temperature of the gaseous C02 from -78.0°C to the final temperature of the coffee. 013015: 8 ATS” maas 30.5 “(H003(085077%Q(T‘—-730t> OOSL‘ kT(T,c+7BO ‘19:) . KL—Cam. also U58 Kahlua. Chem 208, Spring 2008 Problem Set 1 Due Friday, Feb. 1 at 2:00 PM o) Calculate the final temperature of the coffee in °C. a 60%: : mCO‘F‘Fea Scuff—tee. bl—Co‘F'Fee = (200.09) (LHE'T/a 0C) (T? , 950 OCB = 0.832, L—J (T; -9553 Ear 44x15 Problem) 50L 1* CL 3as+ icl¥¥cgi O 7%, k3" +0.03kJL('—rF +72.o)L7+ O.?%(E-95.o)kf)‘=o 7.90:. '1‘ 0.0?)ng +2-(95‘t‘ 0.8307“; #dqlq120 , WOT —ga.31 =0 2 *— 268.81: lo 03 ; >|F 0370 7CHC d) Calculate the value of AU for the C02, assuming an atmospheric pressure of 1 atm. (260 mmHg). 00: —Peerx;~.\/= - RTAH : _(8-3lq 37hmbl K} (273,1+7Q))K(O qoq‘MofES) —; — 2 LLC) 3” .% +5.34 k3": 13.3015? §u= c1331 ) " 53° 2‘1:I0.Lk3' e) You taste the coffee, and find that carbonated co ee isn’t very appealing! So you buy another 200.0 m cup of 95°C coffee, and add 40.0 grams of regular (water) ice, initially at -15°C. The final temperature of the coffee is 65°C after the ice melts. Calculate AU for the 40.0 grams of added material. fiCcWCe :- may—ska 303% aTc:a‘$‘R—1& 16—. = (200.03)(H.183760g§(Fgggc)(}owi>= ~23k3" Hart austew Channel ” O Ciaddetnmq‘itl 2.: +28k? AU: “FL/Cl w = 0 Since 5V=0 = 291:3“ 1) Explain briefly the origin of the difference in effectiveness of cooling coffee using -78°C dry ice vs. -1 5°C water ice. USRnS L103 0? ice) ‘m‘rl-Tafla ad— ”‘f§°C 1., Salome: — 30°C USEn5 Ltocj a“? drflauflmtnflaa J ”75‘ (13 01,542,; ~15}: °c m [aware clifirenet? has ‘fwo aerial/1:3: L3- UJALCF has 0x much '0: r"- I) 5142.09) )SHZO C?) > SCOZQCJ) # SFQCia‘Q. Ree} CaPaCrLb Em Coir bark CHOK'CLQ- 2..) Far Li-OS H20 ”Hap: 14,410 -.-_ 2-21mule3 => Jrke l’tea.+ “LJ‘OI’L’QJ 'm Mafia? Wanna} 'H-e‘EO ftp, * (goth? , M, :13.qk’5.HoLm/er flab—“2+ 50 c ‘LS /ml\gz.zzm13) ( 0:23—1:15— absorbed ‘0 SUHIming ‘10? U'FC L (0.90molei) 'IS ofijéfin} of?!) weal: C15ub+clgqs = éfka—X'l' 0.039 kTflqJflBO) ...
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