EXAM 4 Chm 104

EXAM 4 Chm 104 - CHM 104 Rob McGatf Fall 2007: Examtll...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHM 104 Rob McGatf Fall 2007: Examtll (form A) Name: if E Instructions: 1. This exam consists of five pages, a periodic table, and a table of standard reduction potentials. If a page is missing, notify your instructor immediately. Be sure to write your initials on every page after this one. 2. The exam should be completed in 50 minutes. Budget your time, and be sure to answer the questions you know how to work first. Part | is worth 48 points. Part II is worth 18 points. Part Ill is worth 34 points. 3. Record all multiple choice answers on the key below. 4. Try your best, and good luck. 1. r 2. r 3. r 4, f 5. r 6. 7. r 8. r 9. r 10. r ' 11. [E] 12. r l-é '. C—Q.~Q_C~d —4\ $111 e~C—Crc—‘V—b t . . . Part I: Multiple Choice. Read the questions carefully and examine all responses before choosrng the best one. Circle your answers, then mark your answers on the key printed on the cover page! Only this key will be graded. Twelve questions, 4 points each, 48 points total. 1. Which of the following are necessarily true for an endothermic chemical reaction that is spontaneous? a. Aern is positive b. Aern is positive N0 A G : ~ T A S 4? a c. The reaction will be more favorable at higher temperatures / ____, d. all of the above 47 aandcabove r+ MVST‘ (35 1 f. none of the above ' 2. An oxidation-reduction redox reaction has a very large equilibrium constant. From this information, we may ‘nclude with certainty that: éthe forward reaction has a positive standard cell potential \/ ‘E : 0k K ' b. the forward reaction has a positive AGorxn N (5 cu" ‘A a, c. the forward reaction creates electrons L) o l w . all of the above I d e. a and b above 1‘. none of the above In HCIO4, the oxidation number of Cl is: +1 Cl 0 +2 , -1 J J: l? .4} A? ,7— W 0579’?) 6 d.-2 a...‘ +7 . none of the above f.' none of the above 5. The products of the electrolysis of molten Calz are: a. Ca+ and 12- b. Ca2+ and 2|- A c. Ca and 2| Ca and I2 4/ 9" e. Ca2+, 2i-, and 2e- f. none of the above 6. Which of the following metals could theoretically be used as a sacrificial anode in the cathodic protection of iron? a. Sr 1/ b. Al / A .u '~1‘-rH1~ c,— wrm A wort E Fong-WC c. Cu d. Ag (gt—Rum {Lg amh’i‘l’fip Pate/um L e. any of the above and b above Sam/€~Qrc§»—Y 7. A double bond between two carbon atoms is formed using: a. sp orbitals and sp2 orbitals b. sp3 orbitals and sp2 orbitals c. s orbitals and d orbitals C D _l V. Q d. p orbitals and sp orbitals Q _, @p orbitals and sp2 orbitals ON (V M t. sp3 orbitals and duct tape ( 5F'1\ 8. How many carbon atoms are there in 2—methylpentane? a. one b. five ‘ I ix \ g C. geven “\C—C—C’ C“ k”— A e. nine i l l l \ f. thirty-eight bazillion R C a 9. Which of the following factors, above all others, accounts for the observation that there are more carbon compounds than there are compounds of all of the other elements combined? a. carbon’s ability to exist in all three states (solid, liquid, gas) b. carbon’s ability to gain and lose electrons equally well C @ carbon’s ability to form rings and chains v,- d. carbon’s low cost e. carbon’s low density f. the fact that the symbol for the element is C, which is also the first letter in the word “cookie” 10. Reactions that occur in Voltaic cells always: a. produce electrons " b.’ consume electrons (~ @ave positive cell potentials (Ecell) '/ d. have negative cell potentials '” " e. are endothermic f. none of the above 11. Spontaneous chemical reactions always: a. increase the energy of the reacting substances b. decrease the energy of the reacting substances _F c. increase the entropy of the reacting substances d. a and 0 above ‘— e. b and 0 above @none of the above 12. Compounds that contain benzene rings or similar groups are called: a. aliphatic aromatic c. alkanes b d. alkenes ,c/ e. alkynes f. a,c,d,andeabove eec-C. —— C~¥rb Part II. Short Answer. Answer the questions in the space provided. Three questions, 18 points. 1.{5} Write out the cell diagram for a Voltaic cell employing a Pb electrode in contact with 1.0M Pb(NOa)2 and a C0 electrode in contact with 1.0M Co N03)2. 069‘ P5144IC‘ "b P5 :“Cnlg CO | (101+ P514 ~\)S* C014 ile‘ +C6 ‘O-lg MOE 2.{9} Write out the halt-reactions and the overall cell reactions for the electrolysis of molten CrCla ATTHEANODE: lab —-’9 CJL * 13 1+ ’ ATTHECATHODE: Cr +38 ’4’ Cr~ OVERALLCELLREACTION: éClF-‘l 10—34 ’5; "$02 4 'ZCr‘ 3.{4} Draw a sketch of 4-ethyheptane, indicating the positions for all of the atoms. i \ \ l ‘ I _c_—— c— C‘- CP C“ C’C/ ' i l t l ‘ l ,c-4 ‘u ,c- Part III. Problems/ calculations. You must show Iall of your work to receive credit. Your reasoning must be clear. Draw a box around your final answer, and don’t forget to express your answer in the proper units and to the proper number of significant figures. Five questions, 34 points. , F; +’ + e ’ "b \4. t. {6} Calculate the mass of potassium that can be produced by passing a current of 3.44 Amperes through molten KI for 7.41 hours. :2.Lll/L( 7‘ GOM‘ ¥ (:0? ._ — 2. Consider the following reaction: A|(s) + 3Ag+(aq) ——> Al3+(aq)+3Ag(s) ’O a. {4} Calculate Eocell for this reaction ' ' Lev\ Ox '. M AMP”? new 4» O.%C>U QED E El»; 1:76" .5 3M3 A l '13 _¥ 4.3% b. {6} Calculate Ecell for this reaction if [Ag+] = 01000 My [Ala ] = 1.800 M’ and T = 25.00 “C. E :. E“; 001:?" jKéi M‘s Q ELELL: 1*Llcv ' 0.07:5?“ J‘AA WCC . /A La Ai\\j? Ll IL 4. {4} Calculate the standard cell potential for an oxidation-reduction reaction for which AGOrxn = -237kJ, given that there are two electrons in both the oxidation and reduction halt reactions. 0 I. ’_ . ’ ) Aél‘MffiZ:37A/O A Gr: = -V\ Fig-2:“ ac, - My”? m' ~ 1.3:}x/6’g‘7 ‘ 2.474 (214,500,7‘NM/~ ;¢ --7_ .41 43 1’ .5 5.{7} Balance the following reaction occurring in acidic solution: Cr2072' + Fe2+ —‘ Cr3+ + Fe3+ ;(3 '7, Cr T) O lbw iZL] 4714 / i CHM 104 Rob McGaft Fall 2007: Exam N (form B) Name: k1 Instructions: _ , 1. This exam consists of five pages, a periodic table, and a table of standard reduction potentials. It a page is missing, notify your instructor immediately. Be sure to write your initials on every page after this one. 2. The exam should be completed in 50 minutes. Budget your time, and be sure to answer the questions you know how to work first. Part I is worth 48 points. Part II is worth 18 points. Part III is worth 34 points. 3. Record all multiple choice answers on the key below. 4. Try your best, and good luck. multiple choice answers: d 1}} d e f {3 10. a b d e f 11. a [a d e f 12. a b d e ire; ‘. Civm~e « Q— d” :i‘ 1H7, ‘. C~E w(j -~C~l> mt} Part 1: Multiple Choice. Read the questions carefully and examine all responses before choosing the best one. Circle your answers, then mark your answers on the key printed on the cover page! Only this key will be graded. Twelve questions, 4 points each, 48 points total. . 1. ln HCIO4, the oxidation numberofCl is: *‘ "1‘ -7~ a. +1 b. +2 H C c. -1 Q d. —2 e. +7 f. none ot the above 2. An oxidation-reduction reaction has a very large equilibrium constant. From this information, we may conclude with certainty that: / (6:?) the forward reaction has a positive standard cell potential V . Q, b. the forward reaction has a positiVe AGorxn NO E CELL " CL C. the forward reaction creates electrons N C} l d. all of the above ' e. a and b above f. none of the above 0 I 0.1% A Jada J 3. Which of the followingare necessarily true for an endothermic chemical reaction that is spontaneous? a. Aern is positive ‘/ b. Aern is positiveUC , _ 7- IN _ E: c. The reaction will be more favorable at higher temperatures 1/ b ' A“ T A g ' _ d. all of the above "/" a and c above + f. none of the above go 4. The standard cell potential of a Voltaic cell employing a standard h"drone" electrode n. in 1.0 M Al(NOa)3, along with a salt bridge and all other necessary H I a. new 3| “ C 54-35%? cm I 'Z N a, 1m ” a t, a. m . 4.98V , k . 6. 3.32v RED . Whee— “7 ‘3 HL f. none of the above W,.._..~M—a-m-,._ .... m. 5. The products of the electrolysis of molten Calz are: a. Ca+ and I2‘ b. Ca2+ and 2|- A c. Ca and 2| ‘— @Ca and l2 / e. Ca2+, 2l', and 2e- f. none of the above 6. Whircyfi the following metals could theoretically be used as a sacrificial anode in the cathodic protection of iron? a. Sr b. AI / c.Cu g.“ I . - ‘F d-AQ AUH’TH'ZBU (is WLLtH A merit e. any of the above T“ @‘a and b above Po: "7 3Tb IV the i’2 to 0x it: tban Pare mi'TT’l‘rfi K G'“&,’“€"‘C“d‘$ ' 2 7. How many carbon atoms are there in 2-methylpentane? a. one b. five ‘ t l \ ‘3 Q QZven "N C... c.” L... Q___ v“ ' e. nine 1 i i l f. thirty-eightbazillion N C f t A double bond between two carbon atoms is formed using: sp orbitals and sp2 orbitals sp3 orbitals and sp2 orbitals c. s orbitals and d orbitals {/73 orbitals and sp orbitals C5? ’“1 Q .1; Q (a orbitals and sp2 orbitals l/ (3‘ Q9 LP \ V’- f. Sp3 orbitals and duct tape L g E;fi:\ 47 57?)?” 9. Reactions that occur in Voltaic cells always: a. produce electrons b. consume electrons ( " @have positive cell potentials (Ecell) d. have negative cell potentials e. are endothermic t. none of the above 10. Which of the following factors. above all others. accounts for the observation that there are more carbon compounds than there are compounds of all of the other elements combined? a. carbon’s ability to exist in all three states (solid, liquid, gas) ‘ b. carbon’s ability to gain and lose electrons equally well C/ rat’Carbon’s ability to form rings and chains w . carbon’s low cost a nar'hnn‘c inw fiancth w. um...” . vu-uv..y. V I t. the fact that the symbol for the element is C, which is also the first letter in the word "cookie" 11. Compounds that contain benzene rings or similar groups are called: a. aliphatic aromatic \ c. alkanes > d. alkenes ‘% e. alkynes t. a, c, d, and e above 12. Spontaneous chemical reactions always: a. increase the energy of the reacting substances b. decrease the energy of the reacting substances ‘F 0. increase the entropy of the reacting substances d. a and 0 above -/' b and 0 above @one of the above - Cvesg “Crk'vi Part II. Short Answer. Answer the questions in the space provided. Three questions. 18 points. HS} Write out the cell diagram for a Voltaic cell employing a Sn electrode in contact with 1.0M Sn(NOs)2 and a C0 electrode in contact with 1.0M C0(N03)2. ' CC: i C014 H§n14 ‘g t'\ . 2.{9} Write out the half-reactions and the overall cell reactions for the electrolysis of molten AlBra ATTHEANODE: 2Y3; 9) gr?" 4 1e ' ATTHECATHODE: (“3* Jr “3&"Eb R1 OVERALL CELL REACTION: 2 M34 .4 “Sr” ‘4. 1m 4 ‘g ‘3‘. 3.{4} Draw a sketch of 4-ethyoctane. indicating the positions for all of the atoms. Part III. Problems/ calculations. You must show all of your work to receive credit. Your reasoning must be clear. Draw a box around your final answer, and don’t forget to express your answer in the proper units and to the proper number of significant figures. Five questions, 34 points. x ,4 .. ~ LI ‘1: I a "—9 I 1. {6) Calculate the mass of lithium that can be produced by passing a current of 0.77 Amperes through molten LiCl for 1.46 hours. 2. Consider the following reaction: Al(s) + 3Ag+(aq) ~> Al3+(aq) +3Ag(s) a. {4} Calculate E°ceu for this reaction ,E:______ or, m .4. in“ --l }e,/ + m.) e v i x” . z 4 RED ,3A3 “(75% gagcb ‘E -: 1+st ~- j“ (igfmofll Rt: (5;— NM (A L. LU LAT Oil 4. {4} Calculate the standard cell potential for an oxidation-reduction reaction for which A60an = -144kJ. given that there are two electrons in both the oxidation and reduction halt reactions. 6 is S" A (7 "vi ~ ~llqu‘HO j . C . (.3 A (Tr-M > "‘ “rifting Ea _ * Aerriwx (HELL ‘ V\ F __ inqqi‘OSfi ' anglqmw ‘lv-‘~74\ ' .1 4'3 1K 5.{7} Balance the following reaction occurring in acidic solution: 8507? + Fe2+ -' Cr3+ + Fe?“ ax: l—eL Mb Fe“ Ti may allot-77" “‘t C“ I » wflomi (73:33:? Fe” a???" T} tzfiib 070:, ' 4 7k 5,“. OI‘TPEN I” /.—'—————+—- , 3». Ox '\ he 4 N “34‘ [DEB Cuzctq‘”+l~iH++é€ 4’20" fifllfi‘zc Ants "ogEfieifL _ 3+ ‘ .a g; FeH 47 éi’e + 8 “3+ _ » , “Ere? mac? ‘4. ~r ‘3} as}? ...
View Full Document

This test prep was uploaded on 04/07/2008 for the course CHM 104 taught by Professor Mcgaff during the Fall '07 term at Wisc La Crosse.

Page1 / 12

EXAM 4 Chm 104 - CHM 104 Rob McGatf Fall 2007: Examtll...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online