CHEN1211Fall06Test2

CHEN1211Fall06Test2 - A 301 MT 0M5 HOUR EXAM II/Version A...

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Unformatted text preview: A... 301, MT/ 0M5... HOUR EXAM II /Version A CHEN 1211 Tuesday, October 24, 2006 Profs. George & Bowman 7:00PM to 8:00PM Answer all questions on the scantron answer sheet by filling in the proper bubble with a number 2 pencil. If you change your answer, please erase the undesired mark thoroughly. Be sure to fill in the boxes for your student number, name and lab section; then fill in the corresponding bubbles beneath them correctly. A summary of the various molecular shapes is given on page 6. A periodic table with atomic numbers and masses is attached to the back of this exam. There are 5 exam pages and 13 questions. The last question asks for the version of your exam. Check to be sure you have answered all the questions. Please note the point values of each question. Usefiil Information: Avogadro's Number = 6.022 x 1023 mol'1 Number of Moles = Concentration x Volume 1 J = 1 kg mZ/s2 1 amu = 1.6605 x 10'24 g 1 inch = 2.54 cm 1 atm = 101,325 Pa 1 Pa = 1 N/m2 1 N = 1 kgm/sz 1 L = 1000 cm3 1 atm L = 101 J 1 11 = 0.3048 m R = 0.082 Latm/(mol K) PV = nRT AB = q + w = q —PAV AH = qp = AE + PAV (at constant pressure) q = C AT q = (Specific heat) x ( Mass of substance) x AT q = (Cm) x (Moles of substance) x AT Aert = 2(Bonds Broken) — Z(Bonds Formed) Aert = 2 (Product Heats of Formation) - Z (Reactant Heats of Formation) AG = AH -TAS STP 5 Stande Temperature and Pressure for Gases: T= 0°C and P=l atm Gas Diffusion Rate at 1/m“2 (7 Points) Based on the various s, p, d and f electron subshells, how many total electrons can be accommodated in the n=l, n=2 and n=3 principal shells, respectively? 3&~4{;—~4€-4—b—~ 4tw—‘H: ,8 (a) 2,6,12 m3 3; .45. 4;;— 3 (b) 2,8,14 P 3’5 “H7- (c) I 2,8,18 ‘ht2, 2? “(i-L.“ “4“?” H; 8 (d) 2,10,18 39 "4*?" (7 Points) What is the ground state electron configuration for the element manganese (Mn)? How many unpaired electrons are found in Mn? (a) [Ar] 4s23d4 4 unpaired electrons (b) [Ar] 4s23d5 2 unpaired electrons ((c) [Ar] 4s23d5 5 unpaired electrons 3 3d; ) ; ‘43 4'59 (d) [Ar] 4sz3d6 4 unpaired electrons r5} (e) [Ar] 4823d7 3 unpaired electrons C V3 (8 Points) Using a Born-Haber cycle, determine the lattice energy for NaCl(s) based on the following reactions given below. The lattice energy of NaCl(s) corresponds to: NaCl(s) —> Na+(g) + Cl(g). Na(s) + 1/2C12(g) —> NaCl(s) -4ll kJ/mol Na(s) —> Na(g) +1073 kJ/mol l/2C12(g) —> Cl(g) +122 kJ/mol Na(g) —» Na+(g) + e‘ +4958 kJ/mol Cl(g) + e‘ —> Cl(g) -348.6 kJ/mol (a) -345kJ/m01 NaC/ (y) ~47 Ma (S) +— Vac]; ‘4/1/ (b) +345 kJ/mol "0 (g) ‘4) ’V“ (3) H0 7‘ 3 (c) +411.o kJ/mol V?” (Q (a) ‘9 (1(9) - :[22 Na(s) ——> Na (3)—¢~e 9955' (d) -787.5 kJ/mol WW” W NaC/ (S) ‘-‘> M¢*(3)+Cl-(9) +787. 5 (7 Points) Based on the following electronegativities, which bond is the most ionic? Al 1.61 Si 1.90 H 2.20 C 2.55 Br 2.96 Cl 3.16 O 3.44 (a) CH (b) O-H 3 '6 - w = '69 my» d*%’enre (d) Si-Cl (e) C-Br (8 Points) Hydrogen cyanide is a highly toxic molecule. Based on formal charge, should hydro gen cyanide be assigned the structure HNC or HCN or are they equivalent? What is the formal charge on the C atom in HNC? (a) HNC H H : C ::: N: (b) HNC 0 7‘ A (c) Equivalent O L/‘(1i3):0 5" (14‘3) =0 (d)HN ...0 H:u:::c: 5-(§3)=H ‘1—(?4*Z)“/ (11 Points) Which of the following triatomic molecules has a shape that is bent? (3) N20 (b) CO v, " .o . a :z 3 s o - (d) Xez (e) Ber " (11 Points) Baked goods "rise" because gases are produced by chemical reactions when using baking soda or yeast. A typical sheet of pastry has dimensions given as: 8 inch by 11 inch by 0.75 inch. Calculate the work done by this typical sheet of pastry if the pastry expands to four times its original volume when baked at atmospheric pressure (P= 1 atm). 3 v gm, x0.7§: 4,9 m3x(2§‘m+> -= x9320: w I 2 "032 L” (b) +3sz 1022:. «~47 4’ BEGA— (c) -438J 4w = 9.326;. - {0221.} 3.2.HW— (d) +438J Ws- Paw = — lam (Bic/Lib) (e) -564J w = — 3,244 amL >< ELK .-.~ ~328J lahnL. (11 Points) CH4 is used to heat homes. A typical home has a volume of V= 4.5 x 105 L based on an area of 2000 it2 and a ceiling height of 8 fi. Assume that the air is composed of only N2 and the pressure is P= 1 atm. How many moles of methane are required to raise the temperature in the home from 40°F (4.4°C) to 70°F (21 . 1°C)? The heat capacity of N2 gas is 1.01 J/ g K. The heat of reaction for the combustion of CH4 (CH4 + 202 —+ C02 + 2H20) is AH = -890.8 kJ/mol. » ‘3 LI Pl/zm/FT ,7: Pv/RT = y/aI-m[4.sxzo 4») 3,3731“, (a) 1.7moles 0.052 1.0%. 277‘”: waits “L. Fitz-52¢ I ' (b) 4.6moles l‘q73x’U‘JWOQ0A/Zr K 25:, Na : giggx ’05“? Hz (c) 7.5 moles NW" N; g, -- -— CmflT 2 ha! I '(ff‘fxlasag) (167/6) = ?«?“/’<'0 r (d) 10.5 moles ‘2,’ 9K. ' w ' (e) 13.8 moles 6y, 3 so: Ioéf :2. tag Matias: 15.?” 89cm We (8 Points) What is the heat of reaction for the reaction: 2 FeO(s) + 1/2 02(g) —+ Fe203(g) You are given the heats of formation for FeO and Fe203 given below: Fe(s) + 1/202(g) —+ FeO(s) AH = -266.5 kJ/mol 2Fe(s) + 3/202(g) —+ F6203(s) AH = -824.2 kJ/mol (a) -137.5kJ/mol 2550(5) -'-—'> ZF€($)+- 02 (6,) #5393 b-291.2 kJ/mol A ZFE (y) + Z 02 (3) .9 page} (g) - 829; a (c) -422.2 kJ/mol gym 2 papa) + 520$ny Féaas (r5) -ZQAZ (d) -557.7 kJ/mol (e) -624.1 kJ/mol IO. (7 Points) Equilibrium is defined as the state at which AG = 0. For a reaction with AH = -33 kJ and AS = -58 J/K, at what temperature will the reaction be at equilibrium? .. J:\.. (a)391K Ag:41H~7215:-?3t3'-7’(5“8K,2—~O (b)422K “33000f4- 7/57? =3 0 517K (e)721 Tm: .zaoflgf :z. 5'60“: .95 I? k 11. (8 Points) You are given that 4.0 moles of hydrogen gas (H2) and 3.0 moles of oxygen (02) gas are reacted in a sealed container that initially contains no other gases. The H2 and Oz react to form liquid water (H20). Assuming that there is no water in the gas phase, what is the final total volume of gas when the limiting reactant is completely 9 i reacted at STP. #2 + '4 a; Mac) (a)112L «1a m 3 >2 Mare: art“ as); weak: I, whoa/g l NM "fir (b)157L (brad-3A5) I mole a (C)90.L Pt/ShKT L‘% I 0,: [fing [maQ(0.9$2 waug)(275i€) P NM , ( ¢+M (e) Not within 10% of any of the above answers 22% g 12. (7 Points) What is the ratio of the diffusion rates for hydrogen (H2) gas and helium (He) gas. In other words, what is (Diffusion Rate of H2) / (Diffusion Rate of He)? // V (a) 1.0 2, mm D”?- _ MM.» : i (i=l“f ' 0H3 “’54 " Z (c) 2.0 2" (d) 0.51 (e) 0.71 13. What is the version of your exam? ((a) Version A > (b) Version B ...
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CHEN1211Fall06Test2 - A 301 MT 0M5 HOUR EXAM II/Version A...

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