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chem2exam3 - Chemistry 1302-1 Exam 3 November 10, 2005...

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Unformatted text preview: Chemistry 1302-1 Exam 3 November 10, 2005 MMWAQL— Multiple choice ( polnt§ eggh)‘ Mark your answer on the scantroni Be careful to erase completely if you change an answer. Only the scantron willbegraded. gzhgclg your answers; don‘t be clueless! 1. Balance the following redox reaction which occurs in acid solution: Fe2+(aq) + Cr2072'(aq) —-—-D Fe3 +(aq) + Cr 3+(aq) What is the stoichiometric coefficient for H20 in the simplified balanced equation? 7 ©ch —->C\r¢3+ea-><NW 4* ‘Q tr‘ — B. 11 a if. :"6/ GJHHHWCQOwZ' "$2Cr3h “TWO ? \Zik \E. 41 ‘33 ® ‘ J 7 2. In principle, the reaction of chromium and iron (II) ion can be used to build an electrochemical cell: 2 Cr(s) + 3 F62+(aq) ——-—D 2 C13 +(aq) + 3 Fe(s) or, put another way, Cr(s) I C13 +(aq) II F62+(aq) I Fe(s) In this working voltracircggll, which of the following statements is w? Cr (s) is reduced to C13 + (aq). \B\ Electrons flow fr Fe to Cr through the external conductor. \8\ Fe2+ (aq) is oxidized to Fe (s). Cg). Cr (s) is the oxidizin agent . M““'< 6 y *1 :- Luci ‘r\ - none of the above 5 i 3 c 3. For which of the following cases is a reaction spontaneous from left to right? * o + NM \14: Aern>0 \ _+ 31‘ Nb Ecell>0 ++ \ NT 3w ’ ./ Ecell < 0 H s g D. Q/K > 1 H; (Aern — TAern) > 0 4. la reaction is exothermic and non-spontaneous at room temperature, AHan > 0 w Ecell>0 +6 -—5 ++| ’W<O D. Q/K < 1 ~ Aern.<_ 0, Aern 0 + \3 7k 3‘ G . . . A x _, 1x 5. If a reaction is exothermic and AS>0 at 298K, $0] 5% \ .. _ it can never be spontaneous. MC,h Q / f) it may be non-spontaneous at higher temperatures. Q 'OQQ 1y ‘ . .13; it may be non—spontaneous at lower temperatures. ’5 L) t 4, / x K it may have positive AG at higher temperatures. ( \ 53/. h J ' / E. 6. Two allotropes of carbon are grap ' below at 25°C? For ' - For diamond AH} A. B. it is spontaneous at all temperatures. 0.90 kJ/mol 2.90 kJ/mol -0.9O kJ/mol -2.90 kJ/mol none of the above 7. Hydrogen peroxide, H202, decomposes according to the equation: H202 —. H2O + O2 From the following data, calculate the equilibrium constant for the reaction at 25°C. AHO A. B. @ D. E. = —98.2 k]; AS° = 70.1 J/K A- LG; \g : c 1.3 x 10'21 20.9 _ x1020 DC; A _ ‘ 8.6 x 104 none of the above 8. If AG°mI1 for the reaction shown below using hydrazine as the reducing agent is —607 kJ, calculate free“ that could be obtained from a fuel cell using the reaction. N2H4(aq) + 02 (g) ——'—. N2(g) + 1.23 v _ ‘ 3.14v [X3 r- n? C,e\\ Malls % NLauHu we. 6.29V . I T —3.14v M0 “N t 0L ‘—> ZHLQ 157V (w Kcltflézy 9. Given the cell: In (5) I [n+3 (aq) II Cu+2 (aq) I Cu (s) If E°oeu = 0.68 V and the standard reduction voltage of €qu2 (aq) is 0.34 V, the standard reduction volta e of In+3 (aq) is A. 0.00v B. 0.34v © -0.34v ‘08 ’— Khaki D. 0.68 v E. 1.02 V 10. For a certain formation product, Kf = 107. What are the signs of AH“, AS”, and AG“ for the equation from which the Kr expression is derived? AH° AS” AG" A. - + + B. + - - C. — - + é + + + 11. Describe the following dissolution process at 298K where AHf°[NH4NO3(S)] = —365.6 kJ/mol and AHf°[NH4NO3(aq, 1 M)] = -339.9 kJ/mol; S°[NH4N03(s)] = +151 .1 J/K-mol and S°[NH4N03(aq, 1 M)] = 259.8 J/K-mol. NH4N03(s) ———v NH4NO3(aq,1 M) It is endothermic and spontaneous. H 3 G B It is endothermic and Waneous. \ ‘l‘ x (‘1 S G C It is exothermic and spontaneous. ‘ + . l‘ . x \ D. It IS exothermic and non-s eous. E Not Wis given to solve the problem. 12. For a certain reaction, AG" is -10.0 k] at 100K and -15.0 k] at 300K. Assuming AH° and AS” remain constant at the two temperatures, the value of &° for this reaction is +25 J/K . -25J/K , : f ‘ C. +50J/K '0' '5 * 3005-,003 D. +120 J/K 5 : 1005 E. —50 J/K 3 13. 14. 15. 16. ( Amy‘squ ‘56-9 AG‘} for CH4 (g) at 298 K = -50.9 kJ/mol. AG°f for CO2 (g) at 298 K = -394.4 kJ/mol. AG‘} for H20 (g) at 298 K = -228.6 kJ/mol. What is AG°,,m for the reaction which produces water and carbon dioxide from the combustion of one mole of methane in air? A. B. M?) E. 5721 MW a CM emerge: +800.7kJ -800.7kJ CHt-l + 0'; A +le + CO +201 saw 1 -902.5kJ r we fild‘ L‘ CRH A CQL~$‘Hfi' fig;— 201% CHH A 2.910 + COL none of the above For the reaction A + B —’ C + D , AH“ = +30 k] and AS“ 2 +100 J/K. Above what temperature will the reaction become spontaneous? E: E:\ spontaneous above 300K spontaneous above 0.300K non—spontaneous at all temperatures spontaneous at all temperatures none of the above ++ \ N’t Sd/ What is the cell potential for Li(s) I Li+(aq) I I Ag+(aq) I Ag(s) if the standard electrode potentials are E°(Li+(aq),u(s)) = +3.04 V and E°(Ag+(aq),Ag(s)) = +0.80 V; [Ag+(aq)] = 0.50 M and [Li+(aq)] = 0.10 M? A Given what is AG'},m for .mpo@l> 3.76V (3'3H3‘<X05u . 3.8OV \) (‘03 3.84V 3.88V none of the above F6203 (S) and A1203 (S) —' 2 Fe(s) + 3/2 02(g) Tag. 2 Al(s) + 3/2 02(g) __/ \ AG°m = +742 kJ AG"ml = +1582 1:], 2 A] (s) + Fe203(s) ————v A1203(s) + 2 Fe(s) —2324kJ ' -840kJ +2324kJ +840kJ none of the above 17. In the reaction HClO(aq) + H200) H3O+(aq) + ClO'(aq), Ka = 3.0 x 10‘8 at 298K. What is Air“ when [H30+] = [ClO'] =l.00 x 10“4 and [HClO] = 0.100? A. +42.9 U B. -115 kJ C. —19.9 kJ @ +2.97 k] E. 402 kJ 18. Calculate E’ce" for the following reaction: 3 Sn2+(aq) + 2Cr(s) "‘—' 3 Sn(s) + 2 C13+(aq) Sn2+(aq) + 2e— ——> Sn(s) E“: -O.14V C13+(aq) + 3 e’ ——> Cm) E°= +0.74V 1.06 V 0.88 V —1.06 V A. B. C. 0.60 V E. none of the above 19. Given that the solubility product of AgCl is 1.8 x 10'10, calculate A? at 25°C for: Ag+(aq> + C1'(aq) ——- AgCl(s) A. +4.65 k] _ B. - 4,65 kJ '2 8 300985000 '8 t [04% @ +555 kJ . - 55.5 k] D E none of the above 20. A solution of AgN03 is electrolyzed by passing 1.50 A of current for 30.0 minutes. What mass of silver plates out on the cathode? A. 1.51 g B. 0.014 g © 3.02 g D. 0.028 g E. none of the above 21. What is the Esp for AgI based on the following? AgI(s) + e" —' Ag (s) + I'(aq) E° =+0.152V and Ag+(aq) + e“ —-——' Ag(s) E0 = +0.799V / -17 .\ 2.? Z: 13-13 we C 5.4 x 10-14 D. 1.8 x 10-12 E. none of the above 22. Calculate the equilibrium constant at 25°C for the reaction below: 3 Ag(s) + N03'(aq) + 4 H+(aq) 3 Ag+(aq) + N0(g) + 2 H20 (1) E°(N0;(aq),NO(g)) = + 0.964 V; E°(Ag+ (aq),Ag (3)) = + 0.799 V A. 6.0 x 1029 (is . “New : B. 2.3 x 108 "ii/11.. «a . 6.1 x 102 " 5 ffiu) ® 1.8 x 1027 3V\‘jo\j M E. 2.2 x 1089 A u 5 VA” Hi++ +. lw Q 03 e we. 2“ 23. Construct a cell with identical copper electrodes placed in two solutions. Solution A contains 0.75 M Cu2+ and solution B contains Cu2+ at a lower concentration. Eu” for the concentration cell is 0.045 V. What is [Cu2+] in solution B? A. 0.060 M B. 0.13 M , A 0.38M ‘MS‘ (0&1 to“ 1151 1'7ij 0.023M \ 1 J ~\ >< 1 1? 1. Not enough information is given to solve the problem. 24. What is Em] for the following if E2611 = -0.029 V, and [Fe+2] = 0.015 M, [Fe+3] = 0.35 M, and [Ag+1] = 0.25 M? Ag (3) I Ag+1 (0.25M) ll Fe+3 (0.35M) I Fe+2(o.015M), Pt(s) mm as» + A w + B. - +0.029V <0m — Ogily m c. +0.15V ( m [‘03 D. —o.09v ' 53 E. No reaction will occur. E: H i t "35171) }\ 1/7). 25. Determine the gel] voltage for the reaction shown where [F63 +(aq)] = 0.10 M, [F62+(aq)] T 0.010 M, and [Cd2+(aq)] = 0.10 M? E°ceu = +1.171 V\ 2 Fe3+(aq) + Cd(s) —’ 2 Fez+(aq) + bd2+(aq) A. 1.260 v °‘ 0 \ 1.359 v C. 1.290V “ml “ 0571 D. 1.082 V n\ lo f E. none of the above L' [JC 0!] Z l V‘ L {‘7 1 J 26. Balance the following redox reaction, which occurs in base solution: I'(aq) + MnO4‘(aq) —'—" Mn02(s) + 12(3) What is the stoichiometric coefficient for hydroxide ion in the simplified balanced equation? A. 8 ’- — 12 Z J“ A + 2 ~ @ 4 8% 4 x e D. 6 ' m E. none of the above h‘ 0% \ \Q‘ 3e; \7 / MHOA, a 2 \ ~ L fill‘i \ \) Tfi + #279 Kf 1 $1 7 \ MO C 2 +ZH ...
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This note was uploaded on 04/14/2008 for the course CHE 1302 taught by Professor Young during the Spring '08 term at Baylor.

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chem2exam3 - Chemistry 1302-1 Exam 3 November 10, 2005...

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