Pretest3-Key - CHM1045 Test 3(Fall 2006 version A...

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Unformatted text preview: CHM1045 Test 3 (Fall, 2006) version A Instructor: Prof. Bush J em a KE Y Recitation Number Name (Show all your work. No books or notes are to be used during this test. There are ten problems on 3 pages plus a periodic table at the end. Please verify that you have all pages) 1. a. How many milliliters of3 25M KzCrO7 solution must be diluted in order to Breparg /250mL 0f 1M solution MVF MZV) V: “4sz @ (MQZB‘Oé L2 :(7.(oC?ML/' 3 M. ‘ (3 2531117 \3327 / {VI M( 'J .lf25. 0 mL ofa 5.13M stock solution of KzCr07 is diluted to 235 1111.. what is the A concentration of ther resulting solution? ' I M i/IV: ”‘4sz M2: ‘M V1 , (5.13M)(25.Q,11L/ “LSQQ/V] 2. In order to determine the molar mass of an unknown organic acid. a chemist performs a titration with sodium hydroxide. Calculate the molar mass ofthis acid. HA, assuming 1.246 g of the acid reacts with 26.94 ml, of 0.342M NaOH. Assume that the unknown acid is monoprotic, 100% pure, and dissolves and reacts completely according to the following reacnon: ATM equivalence lHAthH-eA-J'HZO (onC. 7t . Pam'i ear A Monoproht #112“ m5 Mil. . W M- 72 Mkolgj a351~M10l€S 05158 9 O' 02 0/” L XO L xlnv‘EOl-l‘s Mae 8 H74 //., The Mfiwar we? lfl l0 dflfihzli; IS in , 1/ ' ' 19:16:! 139. L1 34% ’ ’ o 009214161111 =L jflaffils 3. At rest. the average pl] of blood is about 7.4. Following strenuous physical exenion, more carbon dioxide (and less oxygen) dissolved in the blood causes elevated serum bicarbonate. resulting in the pH ot‘blood dropping briefly to 6.9 according to the reaction: C02 + H20 —) H2CO; -)H++ HCOJ‘ Calculate the hydrogen ion concentration. [H ] of blood at each pH. pH * 403111 J10 f’”. 11] 3 ‘7‘ p11: 101 1113 L ' \ 1111 12111503 {:09}; 190111 5115;: -9ng 10 — [11*] 4. Using Hess‘s Law and the following reactions and thermodynamic data: 2 (C(s)+02(g) com) AHz=—393.5kJ a}: g H2(g)+(l/2)Oz( 9H20 (l) AH3=‘-285.8kJ + Calculate the enthal .AHm ofthe following reaction “A." 7'fo V)“ ‘3 £40 2C(S) + H2(g) 9 C2H2(g) 1'" "WW— fl - 9wrlfez ‘5 111054.252 Sign; +50 5 /'/ A /’ x ' , _ l A + A ,L . ' C ...... Wm - - w W 1.1 + 2. o. W» 11.5 ----- - _- - x..._a -_M.—..~~~~.__.~__.1M_,_r_-’~flv-“-’ S. / ’ w / L1 , 2L + H2 + (2+g)027,..__> CZ Hl/ 7: (32. 5. Calculate the standard enthalpy change for the following reaction from the given standard cnthalpies of formation. CaC03(s) 9 Ca0(s) + C02(g) ‘ kJ/mol 111% C02(g))= —393.5 kJ/mol PH - l All? 4 /’ AH;0(Ca0(s))=—635.5 kJ/mol ml {’C’q ”/55 5) + Al' £1,021 Ag €462.35; } 1111,91 CaC03(s))=—1207.1 i Ailrxn - ZAH£ Faclucd .. EAH)‘ {1°ch . 1 l .J . Haw): Z~ 5%:ng ”mSFTT” fLIZO7.ll:-Th/1 \ ,{9 f,- 1 “1159.; Mo! K_/‘} 1 \.- ”.1-“ /LWM Ewe/,1 “(”9 6. A 24 7 g piece of copper with a spec1flc heat capac1ty ofO 385 Jg 1']K is heated to 82 5°( and immersed 111 a beaker with 245. 5 ml ofwatcr w ith a specific heat capacity of4. 184 Jg IK'] and a [09.13 density of 1.00 g/ml. that is at 213°C. Calculate the final temperature of the system. 1 \~ a /7 < ‘ ‘7 Meal chdTvr‘ "l 4611 :3 C?” [i * NCAT MUCH,” Qletr .. - 9,45%an L” L? (MwCu "meaca. : + '1 mwcw(lp 1L4»)? .: ~—- [MchCCK<—lilj ”Tlcw); MW CRJT‘? "“‘ {‘4qu Th) "' '— MC“ C{‘( T; + MC“ QQTLCIA Mqu—lC + MCKCCMT€ '” MNCwTiw 4” MCuCzuTlm 7. If I detonated another hydrogen and oxygen gas mixture. but this time in a piston instead of in a balloon we might find that the system would lose 1150 J of heat energy to the surroundings, while simultaneously causi e iston to rise as the hot gases expandt doing 490 J of work on the surroundings. tat would \e the resultant change in internal energy of the system? I 8. What amount of heat would be evolved from the combustion of methane if it reacts completely with 22. 6 U of oxygen according to the following reaction: 9. What is the energy of one quantum of red photons with a wavelength 01‘725 nm emitted from my laser pointer ifthe speed of light is 30 x108 m/s and Planck’s constant is 6.63 x lO"’4Js? I? What is the frequency of these same photons? \V/ 3 \ 0 l: f ‘3" t 2-7Yx/ I7 em: l’lC Kléégwfl l}; {3 Ox/O/m/g V 1 47’77'25‘MX gas ‘3 6 ...
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