Practice Midterm 2 solutions

Practice Midterm 2 solutions - First Letter of last name...

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Unformatted text preview: First Letter of last name Chem 1B Midterm 2 (exam A), Winter 2005 NameM Permz________.. This exam should contain 7 pages (this cover sheet, 4 pages of exam, one sheet of information and a periodic table). Please count to make sure your exam is complete with no blank pages. You have one hour to complete the exam. Show all work and box your final answer to receive maximum possible credit. The exam is out of a total of 100 points. Good luck! . Exam 2 p. 1 I. ' Chem. 13 2005 1) (30 points total) a) (10 pts.)Fill in the blank. i) A W allows ions to flow between the two compartments 0 a galvanic cell to prevent charge accumulation during redox reactions. ii) The half-life of a 'r % __ order reaction is independent of the initial concentration of reactant. iii) The _Lé:c:u_L_ equation tells us how cell potential depends upon concentration of reactants and prod ts. iv) c=3x105m/s. c is the __ in vacuum. v) A M“. speeds up a c emical reaction without being consumed itself. fl b) (6 Pts.) What is the oxidatiOn state _(:1u {girl-fer J7,“ _. Sag/d (w L,“ [4, cg“ 1) Mn in M1104” _"2_ C in. NaZC204 _._.J_3._...___ r"ét/ Gfl-v)|~—(/ a t Br in HBI‘O4 42"— c) (6 pts.) Balance the following oxidation-reduction reaction, which occurs in acidic solution: Cu(s) + NO3'(aq) 9 Cu1+(aq) + N0(g). 3x (Cu “~79” “95) .2x(//q,‘+w‘+3€ 4w +9540) 30 + 21/93” + 3W ___7 3C,” +9/Vo +w§fo d) (8 pts.) True/False. Circle the correct response. iii) Red light has a longer wavelength than blue light. iv) According to the collision model, doubling the temperature for a i) In a galvanic cell, electrons flow from cathode to anode. T ii) In an electrolytic cell, electrons flow from cathode to anode. ‘ C?) _F chemical reaction should double the rate. T Q Exam 2 p. 2 Chem. 18 2005 2) (25 points) Use the following half reaction data in this problem. (All parts assume T=25°C.): ' Na+ + e“ -) Na ‘2.71 A1“ + 3e: -) Al - 1 .66 Fe2+ + 2e' 9 Fe -O.44 Co2+ + Ze- -) Co -0.28 Cu2+ + 2e 9 Cu +0.34 Ag + e‘ -) Ag +0.80 C1; + 2e" 9 2C1' +1.36 F2 + 26 -) 2F +2.87 a) (5 pts.) Which of the followmg is the best reducing agent? Circle the answer. 5hr rag/«£17 93,44," ,3 w: 1‘ «am/Y 04Jo-(r‘f-ecf C12 F2 - Mr F- b) (5 pts.) Silver (Ag) will spontaneously reduce which of the following under standard conditions? ’ ', ‘ - . .1] 1 . nee£@ c) (5 pts.) Calculate the standard potential, E, for a cell that employs the reaction: Co + 2Ag+ -> Co2+ + ZAg. ' 0-?0 ——(—0,,,72') :{1-[03’1/ ; d) (5 pts.) A galvanic cell is constructed employing the Fe and Ag electrodes in aqueous 1M Fe2+ and Ag solutions respectively. Which electrode is the . - 7 cathode and Wthh is the anode. 0' 80 _ (a (I?) 2 0 [J (Elfin/4 Ff cf-fibje' e) (5 pts.) Calculate the cell potential, E, for the reaction of part (c) when [Ag+]=0._3M and [C02+]-=1.2M. £:£a # 0,0972 1.2433] _: [-03 “0.05. =2 //.05‘(/; . .....-.kiu-n..-.nfi‘u._yaufl.ak=-.-:.'"film‘s-arm t... \..i:=7‘. _-_k .m - ‘ -ann'u. ... .. .r. -: .m.'-"-..:'..‘.-- . . t... ......t 2.3 .....l... .. . ..-.k . l _- cu Exam 2 p. 3 Chem. 1B 2005 3) (10 pts.) The oxidation of Ct“ to 003' can be accomplished using Ce4+ in a buffered solution. The following data were collected (all concentrations are listed in mol/L): Relative Initial Rate [Ce4+]o [Ce3+]0 [Cr3+]o 1 .0x10'3 1.0x10'2 3.0x10'2 2 x 4.01:10'3 2.0){10'2 3.0x10'2 4 .0x103 ’1 1.0x10'2 35.0):10'2 16 8.0x10‘3 2.01th‘2 6.07410“2 Write the rate law for this reaction. .1 M4 [(-‘rwj [1,; m” (5-?)4...’ «*5 4hr74 I (£59 I"; n, “(c-7,4,)” ‘—'7 5*44 =>g317 collected: t(minutes) [N205](mol/L) L, [/4015 j / fit}. ’5 C4 0 1.243(10‘2 ‘ .. q. ‘26; 10 _ 0.92x102 _ q. o», 56"”? 4'" 20 0.68x102 -4610! 5"“ ALng 30 0.50x10-2 m '50 ,3 r " i 40 _ 0.37x102. 400 °*"*** 50 0.2mm2 ‘ - g. 55 4 1‘ -0. So What is the order of this reaction in N205? (5 pts.) 4/) 1L O/°/(/'. I Calculate the half-life of the reaction. (10 pts.) F76” ' == *Gflme 27) = M? 12:10: ’93. C {J 5—0-9191 53"“.1 b Exam 2 p. 4 Chem. 18 2005 5) (10 pts.) Calculate the energy, wavelength and frequency of‘a photon that can be absorbed by Hydrogen atom to cause a transition from the 'n———2 level to 11:5. "- '- __ - / a—I- Ac ski—[2 _,.-.Zl?mb ’5'(;{L§_—; J 6) (10 pts.) Electrolysis of a molten salt with the formula MQ, using a current of 3.86 amps for 16.2 minutes, deposits 1.52 g of the unknown metal, M. Identify the metal. OAR/4’51 9:44 or M +/ 5w 4Mch 3. 86/ 2.129. megs” 2 col x fm/e“ X, p.47; [/4 l-«m ?6 :5ng Law/,— I-“IO-Og? cup/M (1(93fiuuol/‘f :rl‘é}{3-/~7 .037 .‘5— I ~- ' I 3%.] ‘" ?«/34s/ ...
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This note was uploaded on 04/29/2009 for the course PHYS 5 taught by Professor Freedman during the Spring '08 term at UCSB.

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Practice Midterm 2 solutions - First Letter of last name...

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