chem final 1

chem final 1 - Practice Final Exam Chem 2C Fall 2007...

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Unformatted text preview: Practice Final Exam -- Chem 2C Fall 2007 Professor Olmstead POTENTIALLY USEFUL INFORMATION is given on the last 2 pages of this exam. Multiple Choice. 3 pts each. Circle one answer. 1. Given: 203 (g) —> 302(g) rate = 114031139321“1 Th overall order of the reaction is 1 ) 2 (c) 3 (d) *1 (6) 0 2. Consider the following reaction: 2N30(g) —:~ 2Ng(g) + 02(g) Given that rate = k[NgO], k = 3.4 x 10"3 s: and the intial concentration of N20 is 0.50 M. calculate the concentration of N20 remaining after 3 .0 min. 0'27M :7" + (b) 0.12M '" =5" / 8’10 .«d/ (c) 0.50 M 3 - 0W F __I (d) 0.99M prloj: 93.4%”? 34, )K/W/av) WM 5: 5 (e) 0.54M .3 “Org/Zflpléqg __ f a: —- 2'. 3 o 5' 3. The rate law for the elementary process N20(g) + 0(g) —> 2N0(g) is _ (a) Rate = ic[N0]2 If 3/} -. W. $5 (:EJJ)’j Rate = kV2[NO] m c Rate = k[N20][O] .. *- Rfltfl = k] w kZENzO] W M W W (3) It isn‘t possible to say 4. Activation energy for a forward reaction is defined as (a) The difference between the energy of the products and reactants (b) The energy difference between the maximum energy of reaction and the energy of the I ducts G? he minimum total kinetic energy that molecules must bring to their collisions for a chemical reaction to occur (d) The total kinetic energy of molecules in collisions (e) The total kinetic energy of molecules in a system 5. In the reaction C4H9Cl(aq) + H300) —:r C4H90H(aq) + HCl(aq) the concentration of the reactant changgirln 0.0562 M to 0.0431 M in 85 see. What is the average rate of reaction over this interval? a :54x104M/s . (b) 1.54X10'4moles Eat/Le: “‘13 [Cr H401] ('3) 154K 1041110168/3 A t d 0.0154M is; 0-0154M/s :2—{00/7‘5/ --* 0.0562. M 35,4 -.-.-.- /.54x/0"*M/fl— 6. How many protons and neutrons, respectively. are there in 1231? (a) 123,, 53 03) 53.123 53 W W ('3) 53,181 /2.E'——55='75_MW 7. The decay constant for strontium-v90 is 0.0247 years—l. How many grams of strontium-90 remain if 10.0 gdecay for exactly 75 years? 59 “M fl m (a) 0.14 g 5" mo (13 0.00329 g MN == —-- A H (c) 1.57g -: gagfgzgf'fg, few/0.2? ) 020g = -— x. 552 + ,2... 305 (e) 63'” .2.- 0.1713; Head's}: /. 575/ 8. The nuclear equation for the disintegration of Np-237 produces Pa—233. What other particle is produced? (a) alpha particle 237 7:33 4 Qneutron a)ng “F?” qua' +ZLH£ (c) beta particle (d) proton (e) positron ' ' W 9. How many unpaired electrons are predicted for [Mn(CN)6]dfi? % fl J (d) 3 W (LN-FM mm - - 1.. Asia?“ (e) 5 ‘ -——--—— -——-—- 0C“ '3 -' ’H’ 1” 7 atqu pix-Eyflfij—z: 10. These three transition metal atoms or ions might be found with electronic configurations having six d—electrons (a) (313+. Mn“. Fa”+ (b Ni2+. Co+, Pa2+ Fez: C03: Fen (d) (319+. (31:0. Pa2+ (e) Ni‘”, Cu“. Zn6+ 11. Given: Mn04_(aq) + 110(an + 011an —:> Mn2+(aq) + Clg(g) + H200) If the coefficient of MnOJ in the? balanced equatiEn is 2, how many electrons are tramsferred in .1— the react' I - ’P _ 10 M “ 0?‘ M“ 1+ (13) 5 (c) 2 5 {a '— (d) 7 (6) 3 12. The analysis for iron is usually done by titration with permanganate. Identify the oxidizing agent in the following equation: Mn04'(aq) + 5 Fe2+(aq) + 3 H+ a 5 Fe3+(aq) + W2+(aq) + 4H20 2+ _ __ +2.. fig 55+3H++M7170a ——~——>.r Mn” + 4&0 c -- H+ h MM Lia, ‘ W WJHW/ (e) Fe“ W 54/ MM my 13. The molecular geometry for CO; is (a) trigonal planar -. (b) trigonal biyrarnidal “O 3 Qfl g c bent 'i‘ linear (e) trigonal pyramidal 14. Choose the incorrect answer. The rate of a chemical reaction (a) is often increased when the concentration of one of the reactants is increased (b) is dependent on temperature (c) may be increased by using a catalyst ill be very rapid if the activation energy is large (e) describes the change in concentration of a reactant or product with time 15. [4 points] (a) Draw all the isomers for the square planar complex [PtBrCl(NH3)2] and identify them as either cis—, trans-. Circle any optical isomers. ) / W W?) M73 W - fiW " 16. [4 points] Assuming that the loss of ability to recall what you studied for the 2C final is a first-order process with a half—life of 6.5 weeks, what percent of what you studied will you remember a year later? (Assume you never pick up the book again). 17. [15 points] Three experiments at constant temperature on the initial rates of reaction for the following reaction are tabulated below. N043) + 00(g) —> N0(g) + 002(g) Run [N02]... M [CO]... M Rate, Ms:1 1 0.15 0.05 1.4 x 10‘3 2 0.30 0.05 5.6 x 10'3 3 0.15 0.30 1.431103 a) What is the rate law expression for this reaction? _ I a “L (W WC, b) What is the order of the reaction? 2 0) Calculate the value of k (include units). W W / 18. [10 points] The reaction given in Prob. 19 was studied at two elevated temperatures to determine the activation energy, Ea. From the data given below. calculate the activation energy (give units). Experiment T, K Rate constant k. M"ls'l 1 600 0.70 2 700 21.8 / ,M/M =2: £4: “r” H 3:: 75‘ R I ,za ___,/.... WV» :- EA” .. .. (0W H m K (9.70 $.5II-fJ/ywo/C (K, 7 19. [12 points] Given the mass of chlorine-35 is 34.9639 11., (a) What is the mass defect for chlorine-35? (Exclude electrons from this calculation). Give units. [afcx :3) 27m 07X L0075’a) r'K/fitx /.0'0<§7m) /3 =- 35.2.sezt/t mm W :— (5%‘ieH-v-55‘a'2/c‘t’72/Dm 3 —— 0 3203 LL (b) Calculate the binding energy in J for an atom of chlorine—35. Give units. 33W ” “fittirgwa— /évéc?S’ X/0"2’7 At. ,z 032.05%:- gé/S’éwb if (d) Calculate the binding energy in J per gram of chlorine-35. -- H 13 {5 4.780 X/ttfjjmwx sozzxw W“ 28734”) 20. (12 points) The following mechanism has been proposed for the reaction of Hg with 1C1 in the gas phase: His) +1Cl(s) —> 141(3) + HCKa) Hlts) +1C1(s) —-> 12(3) + HCKg) (a) Write the balanced equation for the overall reaction H915) + ZIC/I/g/D —~7 I21?) + grim/My) (1)) Does this reaction have any intermediates? If so. what are they? 16PM H I C j/ 3 (c) If the first step is slow and the second one is fast, what rate law do you expect for the overall reaction? f A 01:7 21. [8 points total--each is worth 2 pts] Complete and balance the following reactions using net ionic equations. (a) Na(s) + H200) a 2. Maj/L) 1" ngfl (/4) H? lNfl/+[ (b) CaEYaq) + sofraq) 4» was 0/71 (4/) (c) A solution of zinc nitrate is mixed with a solution of sodium sulfide to form a precipitate. 2": ZI¢Z+[%) t” 5 —7 ZVLS (m) (d) A precipitate of magnesium oxide is dissolved using hydrochloric acid solution. My? («49 t if“ (Mg—7 M3/Z“+[Ap + Rafi/«5) 22. [15 points] The following electrochemical cell can be described by the unbalanced equation. (312072“ (at!) + H+(flq) + 1161(1) —} (313+ (at!) + 12(3) + H200) A solution containing K2Cr207 and H2804 is in one beaker and a solution of KI is in another. A salt bridge is used to join the beakers. The electrode in both reactions is a Pt wire and they are connected with wires through a voltmeter to detect a current. ‘- (a) Write the balanced half reaction for the anode (leave K“L and 8042‘ out of the half reaction). ailmffij/j «a, 11/4) -/' 215“ (b) Write the balanced half reaction for the cathode (leave K+ and 3042' out of the half reaction). Mir-PPM?) 7P C3072FM?) + éae. Illa-‘— (c) Write the cell diagram. Pr (4) / fag.) / 1502/) l/ at; 07%?) Hitler); amp (g ...
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This note was uploaded on 06/21/2008 for the course CHEM 2C taught by Professor Endrle during the Spring '08 term at UC Davis.

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chem final 1 - Practice Final Exam Chem 2C Fall 2007...

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