exam1_sp07 (kummel)

exam1_sp07 (kummel) - chum ‘06 : Kude Test 1: 2007: FILL...

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Unformatted text preview: chum ‘06 : Kude Test 1: 2007: FILL IN YOUR STUDENT ID NUMBER, NAME, AND TEST FORM=B FOR NUMERICAL QUESTIONS CHOOSE THE CLOSEST VALUE (R = 8.314J/mol-K = 0.08206L-atm/mol-K) You may not be seated next to a friend. You may not use a big screen or graphing calculator. One sheet of notes only. I. Calculate the enthalpy of reaction of 28(5) + 3H2(g) 9 Ell-Mg) from the following data (A Kim Jung ll special- -- hint you need to ivide a few stoichiometic coefficients) 3204s) + 3H20(8) -> BzHe(g) + 393m) AH = 2035“ [3, 3H20(l) -) 312mg) AH = l32kJ 3) 02(g) + 2H2(g) -> 211200) AH = -572kJ - 1 58 (a) I. : . s) + 395(g) 92132035) AH = -2546kJ - i 1 1 3 36kJ; (b) -36kJ; (c) -951 k]; (d) +951 kJ; ref-1237 kJ 3/0 mm. « 5" '10 —’)~, n/o V1 4 1M; 4).»4’10 a?) «21/5, .7 351%; 2 Estimate the heat of formation for octane, Cal-Ilsa), in kJ/mol given Al—lc (octane) =AA-A5‘47l kJ/mol at 298K,. AH.(C02) = -393 kJ/mol and AH.(H20(1)) = -286 kJ/mol (a) between 666 and 333;/(b) between 333 and 0; (c) between 0 and -333; (d) between -333 and -666; (eflhere is not enough information to make the estimate 3. Which molecules should have the highest molar heat capacity (CV). N¢(g) at low 298K, N2(g) at 500K , C2H5OH(l) at 298K; or C2H50H(g) at 50 . Read all the answers./(a)’Nz(g)‘ at low 298K; (b) N2(g) at 500K; /(p)’C2H50H(l) at 298K' 2H50H(g) at 500K; ' (e) 2 or more are tied for the highest molar heat capacity. 4 Calculate the AH° in kJ/mol for the following reaction using the given bond energies in kJ/mol. (C-H = 414- F = 155; H-F = 43 l, C-F = 485). CH4(g) + 4 F2(g) —) CF4(g) + 4 HF(g) (a) 4600; b) I390; (c) -1680; (d) 4540; (e) -l420 5 The combustion of graphite in 02, can occur under constant volume or constant pressure conditions. (note |x| means absolute value and AH.(C02(g)) < O). In reference to the combustion of graphite in 0;, which statement is most accurate: K (a) the reaction is exothermic and |AU| << lAl-Il; (b) the reaction is exothermic and usually |AU| >> IAHl; (c) the reaction is endothermic and |AU|< < |AH|; (d) the reaction is endothermic and IAUI >> IAHl; (e) the reaction is exothermic and |AH| ~ |AU| 6. A certain gas expands in volume from 2.0 L to 24.5 L at constant temperature. Calculate u - heat, q, if it expands against aconstant pressure ofS atm. (a)-I 13 J; (b)-l.24 x 10‘ J; (c)-l.l4 x Io‘ J; (d) 113 J .14 x10 1 (A ’ — J \j I’ fear; ,- e ‘7!“ J/M‘ “ _ 1| $23 3" L " .oszoe F31...) ‘ 7 When I535 g of ompound X (MW = 32 mol) was burned in a constant-volume bomb calorimeter, the water temperature rose from 20.27 °C to 26.87 °C. If the mass of water surrounding the calorimeter was exactly 1000 g and the heat capacity of the bomb calorimeter was 1.75 kJI°C without water, calculate the molar heat of combustion at constant volume of compound , The specific heat of water is 4.l84 J/g-°C. (hint you need to combine the heat capacities) )a)18.2 x 105 kJ/mol; -820 kJ/mol: (c) -l .9 kJ/mol; (d) 1.9 kJ/mol; (e) 820 kJ/mol ’ 2‘04? 44.9-1010 AH<ZA (1'5er ‘ ~ 71' ""CC ‘,C_ +lmj‘(4\l8¥.o‘31q)—_ :‘ '5 9 .1 \cj '0‘ «$41313 _, -gtgr—q’ 8. An unknown mass of Iron at °C (C,=0.449 J/g-K) is placed in 100.0'god'i‘water (C, =4.184 J/g°K) at 00°C. What is the mass of the iron if the final temperature islé‘WC? (a) 140g; (b) 2.6g; (c) 26g; ((d) 260g; (e) 66.6g ‘m(.qw\)(w'v5‘3|) ; {0'03 (qugthgkj 07>” '— «file'ést’l/ v310€ 10. ll. l4. l5. l6 IT. 18. l9. On th basis ofthe relatifle‘strengths of intermolecular forces, Which order of enthalpies of vaporization is correct ,(a CHPCd-lehFe; . b_))C5H,OI~i >Ar>NaCl; (c) Manchu? N; (d) NaBr > cnacfin.S ' (c) KCIPCOH6> w Using lattice energies toselstimat‘e bonding strengths, which ofthe following should have the highest boiling point: (a) mcs: (b) no; (drama; to MsO; (e) N: Why are the entropic fvaporization of most liquids the satne { -— 9OJmeol)? (a) Enthalpies ofvaporization are about the same. Boiling points have little variation. (c) All are similar order to disorder transitions. (d) The molar entropies of most liquids are about the same. (e) The product of vapor pressure and boiling point are about the same. _ What is the maximum temperature CaCO3(s) can be heated before it can spontaneously decompose into Ca0(s) and CO;(g)? CaCO3(s) <—-> CaO(s) + C02. At 298 K: AH°f(CaC03) = 4206.9 klhnol; AH0[(Ca0) = -635.09 kJilmol; AliogCOZ) = -393.5] kamol; A1298 K: 30(CaCO3) = 92.9 Jlmol-K; 89(010): 39.75 Ji’mol-K; S°(C02) = 213.74 Ji’mol-K. (a) less than 800K (b) 800 to 900K; (c)'900K to 1200K; (d) 1200K to iSOOK (e) > l 600K Calculate All"; in ltJ/“mol for HgO at 298K given $6, = -ll'i' k] for 2 I-lg(l) + 03(g) —) 2 Hg0(s) and Sfl(Hg(l)) =76.0 Jig-mo], Sq(03(g)) = 205.1 JFK-mol, S g0(s)) = 70.3 KJKK-mol. (careful usually AHT AHOR) (a) ~98; (b) -153; (e) -103;(&1) 91; (e) -l 31 The entropies of formation of N03(g). N(g) and 0(g) are 240.0, 153.2, and 161.0 JlK-mol respectively at 298°K. Calculate the bond energy of NO; in kJ/mol given AG,” = 867.9 k] for N03(g) '9 N(g) + 2 (Mg). (hint, first calculate {ll-IS). (a) 459; (b) 439; (c) 448; (d) 469; (e) 430 Which ofthe following statements is true about gas phase nonlinear molecules: Light molecules have a smaller standard molar entropy than heavy gas phase molecules because (a) light molecules have a higher translationai energy; Might molecules have a lower velocity; .(c)' Light molecul s occupy less volume. ,{dTLight molecules have a smaller spacing between their rotationalr’vibrational energy level , (e Light molecule have a greater spacing between their rotationalfvibrational energy levels L,“ In which oftlie following processes does the entropy ofthe System decrease: boiling waler;@uilding a sand or LEGO castle; (c) the death of an annoying cat; (d) the burning ofa hamburg r on a charcoal grill; (e) shuffling a new deck of cards; Which ofthe following processes has the sign of its entropy change different from the rest? (3 (302(3) '9 (50(2) + “202(2); 03) C0213)? C02(g):-t- (C) C0:(5) 9 C0(g) 4" “302(94- f’ ) g‘(aq) + C]'(aq) -> AlCl(s); (e) dissolving a dead cat in a sulfuric and hydrofluoric acid mixture The melting point ofHCl is -1 l4.3°C and the AH for fusion is 1.99 ltJhnole. What is yrs—AS in Ji’moleK for fr/elezing at the melting point in Jl’mol-K. (a) more than 10; - (b) 10 to l; (c) l to -l; (d)-1 to -10; (e) 'less than -lO {Sillf t__\‘-‘.1t't-’« - -- f t: ‘1 At 298 K the reaction SOClfi (l) + Hp (l) -—> 501 (g) -+- 2HCl (s) is endothermic and AG, < 0. Which ofthe following statements is correct? (a)'The reaction between pure SOC|1(l nd pure water is not spontaneoas at 298 K ; (b) The entropy change for this reaction at 298 K is negative: \e) The entropy change for this reaction at 298 K is positive; (d) The free energy change for this reaction beeorttes more positive when the temperature is raised; (e) The free energy change for this reaction at 298 K is positive A certain chemical reaction has a A 1-1 = -122 kllrnol and A S = 23l Jimol-K. Under what conditions does this reaction proceeds rapidly forward (This is a gommie trick; read the question carefully) (a) All temps; (b) No temp; (c) high temp only (d) low temp only;: e);not enough information given Test Form B Final: .' iv <11 p<n in“ \ 7. 10. ll. 12. l3. l4 Chem 5155 Mammal FILL IN YOUR STUDENT ID NUMBER, NAME. AND TEST FORM=C FOR NUMERICAL QUESTIONS CHOOSE THE CLOSEST VALUE (R = 8.314JIK-mol= 0.08206 L-atmlmol-K) You may not be seated next to a friend. You may not use a graphing calculator. One sheet of notes only. You may not possess or touch a cell phone in your possession during the test. Consider the following processes. (Treat all gases as ideal.) I. The pressure of one mole of oxygen gas is doubled '{sothennally ‘Y‘i 2- 2NH3(g) --> N (g) + 3 H2(g); on 7 0 S 3. Fixing a deck oTcards in order to cheat 5 1r 4. Defragmenting a hard drive on a computer 5 e 5. CH 0H(s) --> CH3OH(I) an : 0 Which 0 these processes leads to a decrease in entropy? (a) none; (b) just one; @ust 2; (d) just 3; (e) 4 or more Se All ofthe following compounds become les ble with respect 0 their elements as the temperature is raised except Lam/0(a): Mame); 02(g) At 101°C, the boiling of water is spon a eous. Predict the sign (+,-, or 0) of AG,°, AH,°, and AS,°, respectively at 101°C. (3) 'r 0: +; -s-)-; @'a+s+; 0543+; (e) 3"? An 7 0 Consider llowing reactionz: NO (g) 9 N(g) + 00;) Which of the following statements regarding this reaction are true? ' he reaction is spontaneous at high temperatures. (b) The reaction is spontaneous at low temperatures; /(23 The re tion is not spontaneous at any temperature. (d) The reaction is spontaneous at all temperatures; M need more information to answer this question mom XY has a higher density than liquid XY; olid XY has a lower density than liquid XY; ((1?) solid XY has the same density as liquid XY; - freezing XY is an endothermic process; (e) XY can never be sublimatcd. For an exothermic reaction, under whi conditions will the enthalpy of reaction be of smaller magnitude than change in internal energy (IAH|<|AU|)? hen moles of product gas are greater than moles of reactant gas; in 7L) , (b) When moles of reactant gas are grea er than moles of product gas; (c) At constant volume; (d) At high pressure; (e) At low pressure; The phase diagram for compound XY has a solid-Ii! id curve with a negative slope. Which of the following is true? seq-:2 Which order of enthalpies of vaporization is wrong? (a) Al > CH30H > CH3CHO; Hg> CH3CH20H> Xe; ,(cf NaCl> CH3CH20H> Xe; pyCH3CH2Ni-l2 > CH3CH2F > CH4;/(e) NaCl > C 3001-13 > CH3CH2NH2 Which of the following has the smallest lattice energy? (a) NaF; (b) Y203; @acl; (d) (NI-102$ (e) Na2504 Calculate the enthalpy for the decomposition of NO; in kJ/mol 2N02(g) '9 2N()(g) + 02(g) from the standard reaction enthalpies of NO(g) -> l/2N2(g) + 1/202 2Nz(g) + 402(g) —> 4N02(g) @114; (b)-247; (c)-ll4; (d)+294; Use average bond enthalpies to calculate APPMM,1 in kJ/mol for 2 H2C=CH2(g) + 2N2(g) -—>2H2C=N=N(g) The bond enthalpies in kJ/mol are(C=C) = 620; (NEN) = 914; (N=N) = 418; (C=N) = 615; (C-H) = unknown; (C-C) = 348; (N-N) =l63. (a) less than -300; (63/300 to -100; (c) -100 to +100; ((1) +100 to +300; (e) more than +300 AH° = -9o.3 kimor' AH° = +1323 kJ~mol" (e) -247 the equilibrium to shift to the right? ddin more SiO ; Increasing the temperature; (c) Adding a catalyst; g . 2 M Decreasing the pressure by increasing the volume; (e) removing water h 70 The decomposition of phosgene, COC12(g) <=———> C0(g) + Cl2(g), is an endothermic rocess. How many of the following factors will cause the value of the equilibrium to shift to left? adding a catalyst; increasing the temperature; decreasing the total pressure. none; b) ne; (c) two; (d) three; (e) four; 5‘49 wka “NC in we The reaction rates of many spontaneous reactions (i.e. K>1 and AG°<0) are actually very slow. 'ch of the following is the best explanation for this observation‘2/,(a)"AS°<<0 ; l(b) AS520; 97} <<K @Q >>K; *6 none of the above ' - afa— ‘ 7" ‘4' Eva {n50 Which 0.0666M solution will be the most basic? {@aflhcoo; KClO4; (c) Na(CHClz)COO; Xi{\C02 (e)Na(CHBr2)COO; r: | "C’C’°"° H —C’C‘-u‘c ‘r( ‘ k H o For the equilibrium Si02(s) + 4HF(g)§> SiF4(g) + 2HzO(g) with AH° = - 148.9 kJ/mol, which of the following would cause we WWI w, 15. Which of the following 1 M solution would be basic (pH>7)/HF,/ a0 a ,WJ, fig? (8) N30“ only; (b) all; (e) NaOH, NaF, NH4CI, KZS only; ((1) NaOH, NH 4C1, K2 (only' 2some 0 combination l6. .hich of the following would you expect to be the ast soluble in H20 and having a boiling point above 200 °C: (a) K/Br; homo, /(.0)’CaBr2; (d)'AgCl; ClI3OH '...l.i.l at - n .l ,t-( 17. Calculate the molecular weight in‘g/mol of a salt X+Y- if a 3.33 g sample dissolved in 666 mL of water has an osmotic pressure of 0.86m at 25.0 “C. (R = 0.0821 L-atm/mol-K ). Assume the solution is ideal. (a)0-50 (b) 51-100; C 101-200; (d) 201-300; (e) 301 or more 4. J o ’r . a 0 . . 18. When a unknown salt is issolved in water, the solutlon becomes colder. This infonnatlon lndlcatez/(aa‘th’e firopy of the solution is negative; /(b’)’ AH of solution is negative; (c) the salt has a small lattic energy c v the solubility of will dec ease as the temperature increases; (d) the solubility of will increase as the temperature increases; Adrme salt probably contains a transition metal c 19- Initial pressures of P(NO) = 0.129 atm and P(Br ) = 0.0543 atm were allowed to react at an unknown temperature. At equilibrium, P(total) = 0.145 atm. Calculate the K in units of atm'l for the reaction 2N0(g)+Br2(g)<--> 2NOBr(g). (a)1xl0‘; (b)6.g; (c)34; 40; (e)51; 20 For PCl;(g) + Clz(g) <--> PC15(g), if the initial concentration of PC15(g) is 6.0 M and the others are zero, at equilibrium the concentration of Clz(g) is 1.60 M. Calculate the value of Kc at this temperature in M". (a)0.6; (b) 3.4; c) .7; (d)0.29; (e) 2.2 71. Calculate the molar solubility of Ba3(PO4)2 in a 0.666M mum. solution. (Ksp = 1.3 x l0'29). (a) more than lot; (b) 10‘ to W; (C) l0'9 to l0”; (d) 10''2 to l0”; (c) less than 10'” 22 Which of the following will in c the solubility of Pb(CN)2(s) (a) addition of 0.1 M HCN; (b) addition of a strong acid; mdition of a strong base; (d) addition of Psz); (e) none ‘ 23. Calculate the minimum number of moles of Mg(N03)z (a strong electrolyte) that must be added to IL of 0.010 M Nal" solution in order to initiate a precipitation of magnesium fluoride. For Mng, K5p= 6.9 x 10‘9. (5)710“ or more; (b) 10"; (c) 10*; (d) 10"; (e) 10'9 or less 24 What is the molar concentration of free Zn” in a 0.30 M solution of [Zn(CN)4]2'? (Kf= 1.0 x 10”) (a) 4.1 x 10"; (b) 8.7 x 10";(@.4 x 10“; (d) 2.4 x 10*; (e) l.2 x 10“ : 7.x3‘rl‘o- 3 2+ 25 A solution is buffered at ab; = 6.66. Estimate the concentrations of Zn in this solution? Zn2+(aq) + 71 H (aq) <..> Zn(CN)2(s) + 2 H+(aq), K = 2.0 x l0'3; (a) l M or more; (b) 0.1 M; (c) 0.0l M ‘. (d 0.001 M (e) 0.00010r less J 3 (a) 0.1M CHCIZCOOH dissolved in 0.1 M HC 04; WELD. 1M CHZCICOOH dissolved in 0.2 M “610;; 26- In which of the following solution will the acid have the greatest percent ionization? (Kim Jon ll loves this one) (c) 0.1M CH3COOH dissolved in 0.1M CH3COONa; (d) 0. l M CH3COOH dissolved in 0.2 M CHJCOONa; VAMIM CH3COOH dissolved in 0.1 M NaClO; W l“: - / 37 Estimate the ratio of [IlSO3f]/[SO3'2] at equilibrium in a 1.0 M H2803(aq) solution (pKnl = 1.81; pK.2 = 6.91). (a) 103 or less; (b) 10‘; (c') 10’; (d) 10"; (e) 107 or more «a -. .utS’ (q I ; 28. Estimate the pH at the equivalence point for the titration f 0.333 M HClOu versus 0.666 M N113. Ki, =l.8 x10". (a) 2 to 4; (b)4 to 6; (c) 6 to 8; (@‘8 to 10; (e) 10 to 12 29 Calculate the pH after 75 mL of 0.40 M KOH as been added to 100 ml. of 0.20 M HZA (pKal = 3.82 and pKaz = 6.10). (a) 4 or less; (b) 4 to 5; (c; 5 to 6; (d) 6 to 7; (e) 7 or more 30. Which of the following mixtures gives a buffer with a pOH greater than 7.0? for CH3COOH, K. = 1.8 x 10" and for 13%, Kb = 1.8 x 10" (a) 6.66 mL of 0.1 Mflfi3(aq) + 3.33 ml of0.l M HCKaq); (b) 6.66 mL of 0.1 M CH;COOH + 3.33 mL of 0.1 M bfa%)H(aq); (6 6.66 mL of 0.1 M CH3COOH + 6.66 mL of 0.1 M NaOH(aq); (d) 6.66 ml. of 0.1 M Nl-l3(aq) + 3.33 mL of 0.1 M HCl(aq): (e) none of these FILL IN YOUR STUDENT ID NUMBER, NAME, AND TEST FORM=C ...
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This note was uploaded on 01/27/2011 for the course CHEM 6B taught by Professor Crowell during the Spring '08 term at UCSD.

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exam1_sp07 (kummel) - chum ‘06 : Kude Test 1: 2007: FILL...

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