Practice Final Answers 2003

Practice Final Answers 2003 - l. Firm] Ema} (8 pts) Use the...

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Unformatted text preview: l. Firm] Ema} (8 pts) Use the following information to determine AH,u of CH3OH (1). AH,“ (kJ /mol) coZ (g) — 393.5 H20 (g) — 241.8 2 CH30H (1) + 302 (g) —> zco2 (g) + 4 H20 (g) AH" = —1277 kJ/mol OH: €(riq3é?) + q{' it‘l-sfl“[3 AHl-ffcilfioél: ' H77 %cl or \J/Wi (9 pts) In class we observed the following reaction at room temperature and pressure: Ba(OH)2 - 8 H10 (3) + 2 NH.SCN (s) ——-> Ba(SCN)2 (s) + 2 NH3 (g) + 10 H20 (1) The solution produced was so cold that it froze the water underneath the beaker, adhering a block of wood to the beaker. Predict the sign of AG, AH and AS for this reaction. Circle the answers. ‘ AG>O AG=0 (8 pts) The major source of aluminum in the world is bauxite, a compound that consists primarily of aluminum oxide. The thermal decomposition of aluminum oxide to produce aluminum occurs via the following reaction. 2A1203(s) 7> 4A1 (s) + 302(g) Given the standard enthalpy of formation of A1203 (5), AHr" = — 1676 kJ/mol. determine how many grams of aluminum will be produced when 1000 k] of heat is consumed. we! (S) 4- 30? £3) 9 911050) ——7 . /, ‘1 .. AH : HWMM]- [Z(—\67a)_} : 3352 H 13::L‘“ ,. , if We at may k3 335.2 k). anoJ 1903 4. (6 pts) Write the reactions that correspond to the following enthalpy changes: 3) AH,0 foradid hydrogen cyanide, HCN (g). N b) AH," for calcium hydroxide. Cars) + oztai+ Hal?) a 0207*“); 5. (6 pts) Write the electronic configuration and indicate the number of unpaired electrons for each of the following species. number of unpaired electrons I electronic configuration 3 3 ( 3 or Islisz’ZP (4 pts) An atom is in an excited electronic state with the electron configuration [Ar]4s23d64p‘. Identify the atom. [qus’347 (’0 a) (8 pts) Draw the Lewis structures, all three resonance forms, for N20, The central atom is a nitrogen Assign formal charges on each of the atoms in all three resonance structures. [6 e‘S 2W"l§-, L. bahds Zr — N:l\?‘ :0-3 w—iis: -’l +1 4-! M —2 b) (3 pts) Based on the assigned formal charges, which of the resonance structures is least favored. 0 E N ~ N c) (3 pts) Based on the assigned formal charges, which of the resonance structures is most favored. Fl sFOrmaJl Charge am him more . electron/egotith MOM“ '5 mm a fowamwkz Firm/f ans Fina/l, 9003 8t (12 pts) CiICIe the formula that best fits each of the following descriptions: . In class we observed the Briggs-Raucher Reaction, causing the solution to switch colors back and forth from blue to clear for several minutes. The reactions that cause the color change are as follows. a) smallest radius Mg Al ‘ A13+ l Cl‘ P ’— 5 1-1202 + 210; + 2 H —> 12 + 5 01 (g) + 6 H20 5H202+IZ —«> 2103‘+2H*+4H10 10 H1020) —> 5 02 (g) + 10 H20 (1) largest ionic radius a) (4 pts) Identify the substance that is reduced in the first reaction. most polar bond T 03 b) (4 pts) Identify the substance that is oxidized in the second reaction. > longest bond length N: I. I 2. Given the following reaction mechanism. greatest electronegativity ' ' B C l 1-1202 i> H20 + M rangf owe/Etc? largest second ionization energy Mg Na Al 916 + '03 VC’i/+ Z 02 /C«l + 9451 —> c5221: a) (3 pts) Write the overall equation for the reaction? (6 pts) Draw the Lewis structures for NO and NO . 2 +1206 4, 0: «.9 +202. : I ‘ u u ' \ .N:Q. :O—NZQ . . r r, b) (3 pts) Identify the reaction intermediate(s). : g - i _ cm, CBC”, Cl u N" i} , 0' c) (3 pts) Identify the catalyst(s)l ,__. b) (4 pts) For which molecule is the NO bond length the longest, NO or N027 Circle the answer. C F a C l a NO NO; (10 pts) One mole of an ideal gas is heated from 25°C to 35°C at constant ressurel (4 pts) At 1 arm pressure and 25“C, the following phase change occurs NZ (1) —> N2 (3) Circle the correct answer foreach of the following quantities: w q AH AE and Ass In the direction written, the phase change is 9 2 5V a) spontaneous at all temperatures A H > L’EO W>0 W 0 W : M P + b) more spontaneous at low temperatures Vt) < 0 @ more spontaneous at high temperatures d) can not be determined from the information given + ll. (4 pts) How many electrons are transferred in the following reaction? 5H202+2103’+2H* —> I2 + 502(g)+6HZO 4‘ 1‘ ‘l FI'AM 2093 , Find 2073 15. Answer the following questions using the data given below: 5 Y‘ F" a ' i 3/ v HalfReaction 50 (V) F to 3 ‘ 4 z e - ~7 Vb — 0‘ l l 5 V annOHm + H200) —> cfiriuoso) +C6H,206(r) Pbi‘ + 2 e‘ —> Pb (s) - 0.125 a W- . i _ , A _ s + Suzi + 2 e. __> Sn (5) __ 0.137 f _.: a . 0 | C v The followmg data and the rate law for this reaction were determined. rate — k [CHI-[non] A7 I 9! 01M [ClZHZZOll](m01/L) lime (hr) Vb” [fl] _- r [C f + 1/1. [9.70 16. The hydrolysis of table sugar (sucrose) to produce glucose and sucrose occurs by the following overall reaction Consider a galvanic cell where Sn(s) is oxidized to Sn” and Pb“ is reduced to Pb (s) at 75C. [:5 id: 0 ‘ p75 0 451 0 50 V . ‘ ‘ y. s ' V . Sn<s)ISn7*|le"|Pb(s) WWW} Wflwnhflm ' pvt} :o/wt 0.353 1.50 ' hth ' :2‘=. 2‘=, _ a) (6 pts) Calculate the initial cell potential, Eamw en econcentrations are [Sn ] 0075 M and [Pb ] 0600M a) (6 P‘s) Use (ms data to de‘emineme ram consmm for this reaction- oy —o.qLi-Qvl7‘?‘) Ax 5 I10 ayfllfifglw Q slypg: slop: : . mew! :~ K I K ,i..i,.Z:-E-ffihL—j 9; "Q , _A v b) (4 pts) If the cell is allowed to operate spontaneously, will 5”“ increase, remain the same or decreases Circle the L1H [mi/Eta j y ‘ k t answer. increase remain the same 6 E N. .‘ y- #e‘. lnfO-LS) c) (8 pts) If the cell is allowed to operate spontaneously, what will 8m, be when [sz‘] has decreased to 0500 M? a ’ Z L! Md”. figmew Wm m , V q Pb1++ Sn —«-;> 5w2++ Pl: I+ ; 5‘7 AJ 0F 13.95 (’9 55C W _ ,-/, a 17. Consider the following reaction. NO (g) + C12 (g) —> NOCI (g) + C1(g) This reaction is endothermic, AH" = 83 le/mol and the forward activation energy, Ex, is 88 kJ/mol. a) (6 pts) Draw a potential energy profile for this reaction‘ Your diagram should show the reactants, products, transition state [X]‘, E3 and AH". d) (8 pts) If the cell is allowed to operate spontaneously, what will [Snl‘] be at the point at which 6”“ : 0.020 V? sz'*.+ SH -—> Snzwet Pb c7 . 6 w x 5». n 75 + x i _g"’“+X‘~ - 0.ozov.: 0~UIZV v "”""In(05 Na+clz Z r + , _, at a 7 5 “ 0, 6 Z 2 .t 'V’ ( O‘Té-L‘w-w Reaction Coordinate (0.6 —x 73(0. 5 35): 3.075 4 x 0 , 2 q 6 z ' . 55 S K b) (4 pts) What is the activation energy for the reverse reaction: NOC1 (g) + C1 (9 —> N0 (3) + (312(3) K: 0.!60 88—83:}5k—TE EMS: aazfi—I x : 0475+ 0.160 )‘HEs'fizzngorzni M] my 0,235 M ...
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Practice Final Answers 2003 - l. Firm] Ema} (8 pts) Use the...

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