CHEM 17 EXAMINATION 1 January 15, 009 Dr. Kimberly M. Broekemeier NAME: Circle lecture time: 9:00 11:00 Constants: c = 3.00 X 10 8 m/s h = 6.63 X 10-34 J x s J = kg x m /s Rydberg Constant = 1.096776 x 10 7 m -1 R = 0.0806 L x atm/mol x K = 8.314 J/mol x K E = -.178 x 10-18 J x (1/n final - 1/n initial ) A = Ɛcl I A 1 1 H 1.008 3 Li 6.941 11 Na.98 19 K 39.10 37 Rb 85.46 55 Cs 13.9 87 Fr (3) II A 4 Be 9.01 1 Mg 4.31 0 Ca 40.08 38 Sr 87.6 56 Ba 137.3 88 Ra 6.0 III B 3 1 Sc 44.96 39 Y 88.91 57 * La 138.9 89 * Ac (7) IV B 4 Ti 47.90 40 Zr 91. 7 Hf 178.4 104 Rf (61) V B 5 3 V 50.94 41 Nb 9.91 73 Ta 180.9 105 Db (6) VI B 6 4 Cr 5.00 4 Mo 95.94 74 W 183.8 106 Sg (63) VII B 7 8 5 Mn 54.94 43 Tc 98.91 75 Re 186. 107 Bh (6) 6 Fe 55.85 44 Ru 101.0 76 Os 190. 108 Hs (65) VIII 9 10 7 Co 58.93 45 Rh 10.9 77 Ir 19. 109 Mt (66) 8 Ni 58.71 46 Pd 106.4 78 Pt 195.0 110 (69) I B 11 9 Cu 63.55 47 Ag 107.8 79 Au 196.9 111 (7) II B 1 30 Zn 65.37 48 Cd 11.4 80 Hg 00.5 11 (77) III A 13 5 B 10.81 13 Al 6.98 31 Ga 69.7 49 In 114.8 81 Tl 04.3 113? IV A 14 6 C 1.01 14 Si 8.09 3 Ge 7.59 50 Sn 118.6 8 Pb 07. 114 (89) V A 15 7 N 14.01 15 P 30.97 33 As 74.9 51 Sb 11.8 83 Bi 08.9 VI A 16 8 O 16.00 16 S 3.06 34 Se 78.96 5 Te 17.6 84 Po (10) VII A 17 9 F 19.00 17 Cl 35.45 35 Br 79.90 53 I 16.9 85 At (10) inert gases 18 He 4.003 10 Ne 0.17 18 Ar 39.95 36 Kr 83.80 54 Xe 131.3 86 Rn () 58 Ce 140.1 90 Th 3.0 59 Pr 140.9 91 Pa (31) 60 Nd 144. 9 U 38.0 61 Pm (147) 93 Np (37) 6 Sm 150.4 94 Pu (4) 63 Eu 151.9 95 Am (43) 64 Gd 157.3 96 Cm (47) 65 Tb 158.9 97 Bk (47) 66 Dy 16.5 98 Cf (51) 67 Ho 164.9 99 Es (54) 68 Er 167.3 100 Fm (53) 69 Tm 168.9 101 Md (56) 70 Yb 173.0 10 No (54) 71 Lu 174.9 103 Lw (57)
PART I: Fill-in the blanks (40 points total) 1) Give the electronic configuration, starting with the previous inert gas core, for each of the following: a. La [Xe]6s 5d 1 c. Ca + [Ar] b. Mo _[Kr]5s 1 4d 5 d. As 3- [Ar]4s 3d 10 4p 6 ) Write a balanced chemical equation, including states, for the following. a. the third ionization enthalpy for Al b. the lattice enthalpy for CaCl (s): Al + (g) Al 3+ (g) + e - Ca + (g) + Cl - (g) CaCl (s) 3) An element has a valence shell electronic configuration of ns (n-1)d 5. a) Its group number (using column numbers from 1-18) is 7. b) It has (metallic nonmetallic) _metallic properties c) When it ionizes, it has a tendency to form a stable ion with a charge of +. d) The highest energy electron of the ground state of an atom of this element will have an l value of. 4) Arrange the following orbitals in order of increasing energy: 4p, 4d, 5s, 5d, 6s _4p < 5s < _4d < _6s < _5d 5) Consider the following pairs of ions that combine to form an ionic solid. Circle the pair in each group of two that would be expected to have the greatest lattice enthalpy. a. K + and O - or K + and S - b. Fe + and O - or Fe 3+ and O - 6) Circle the structure below that is the mostly likely structure? Either the lower left or the middle bottom, both have all atoms with zero formal charge
7) Draw one valid Lewis diagram for each of the following. Show all lone pairs on the atoms. Lines may be used to indicate a bond. a. AlBr 3 (4 valence e - ) c. IF 4 (36 valence e - ) Al is center atom, single bonds to each Br I is center, single bond to each F Each Br has 3 pair of non-bonding electrons Each F has 3 pair of non-bonding e - non-bonding e - pairs on I b. CS d. O 3 Carbon is central, double bond to each S Central O, single bond to 1 O, double Each S has pair of non-bonding e - bond to the other, central O has 1 pair of non-bonding e -, single bonded O has two pair of non-bonding e - and double bonded O has 1 pair of non-bonding e - 8) Refer to the species diagramed in question 7. The shape of the CS molecule is linear, The shape of the IF 4 molecule is square planar. The bond angle Br Al Br in AlBr 3 is 10 The F-I-F bond angle in IF -- 4 is 90 or 180. 9) Draw a Lewis dot structure for ClO 3 (chlorate ion). Also draw any equivalent resonance structures. All structures should have Cl as central atom. Structures ranged from single bonds to each Cl with a non-bonding electron pair on Cl to those with double bonds between Cl and O. Formal charge considerations were used to determine if additional structures were equivalent. PART II: Multiple Choice (4 points total) 1) If each particle below has a velocity of 10 5 m/s, which would have the longest de Broglie wavelength? mass and wavelength are inversely proportional a. proton c. electron e. neutron b. xenon atom d. helium atom f. hydrogen atom ) How many orbitals in a multielectronic atom have n = 3 and m l = +? a. 0 c. e. 4 b. 1 d. 3 f. 5
3) Of the orbitals p x, p y, p z, d xy, d x -y, d z, which have a concentration of electron density along the x - axis? a. p x only c. p x and d xy e. p x, d xy and d x -y b. p y only d. p x and d x -y f. p x and d z 4) Of the following reactions, which one is exothermic? a. Li(g) Li + (g) + e - c. Li + (g) Li + (g) + e - e. Cl(g) + e - Cl - (g) b. Li(s) Li(g) d. Cl (g) Cl(g) + Cl(g) f. LiCl(s) Li + (g) + Cl - (g) 5) Which one of the following atoms has the most unpaired electrons? a. He c. Li e. Be b. N d. O f. F 6) Which one of the following elements has atoms which are the most electronegative? a. Al c. P e. Cl b. Ga d. As f. Br 7) Which one of the following elements has atoms which are the smallest? a. Al c. P e. Cl b. Ga d. As f. Br 8) Which ion below is the largest in size? a. N 3- c. O - e. F - b. Na + d. Mg + f. Al 3+ 9) Which one of the following bonds is the most polar? a. C - N c. C - O e. C - F b. C - Si d. C - P f. C - Cl 10) In the Lewis structure :CΞO: for carbon monoxide, what is the formal charge on the oxygen atom? a. - c. -1 e. 0 b. +1 d. + f. +6
11) The bond length for I is longer than the bond length for Cl. Which one best explains this? a. I is a solid, Cl is a gas d. I exhibits greater effective nuclear charge than Cl b. I experiences greater lone pair repulsions e. I has more electron shells filled than Cl c. Cl has a greater bond order f. I has a greater dipole moment than Cl 1) Which one of the following molecules is polar? a. NCl 3 c. BCl 3 e. CCl 4 b. XeCl 4 d. PCl 5 f. SCl 6 13) How many regions of electron density are around the left side carbon atom in H C Ξ C -- H? a. 0 c. e. 4 b. 1 d. 3 f. 5 14) The molar absorptivity constant (ε) for acetone is 17 M -1 cm -1 (L/mol x cm) at a wavelength of 66 nm. An aqueous solution has an acetone concentration of 0.056 mol/l. If this solution is placed in a 1.00 cm pathlength cell and measured in a spectrometer set to 66 nm, what percent transmittance (%T) will be read? a. 0.95 % c. 95 % e. 5.1 % b.. % d. % f. 11 % PART III: Problems (18 points total) Show your setup, logic and work, and complete three of the following four problems. Place an X through the one you do not want graded. 1) It is known that in the Balmer series of lines in the H spectrum, the lower level quantum state is n =. Calculate the principal quantum number of the upper state for the Balmer line that appears at 410 nm. ΔE = hv = hc = 6.63 x 10 34 J x s (3.00 x 108m s ) λ 410 x 10 9 = 4.85 x 10-19 J ΔE =. 178 x 10 18 1 1 J ( ) with values 4. 85 x 10 19 J =. 178 x 10 18 J ( 1 1 x ) Solving for x: x = 6 n lower n upper
) Calculate the wavelength, in pm, of an electron traveling at 0.0 % of the speed of light. The mass of an electron is 9.109 X 10-8 g. a) electron velocity = (0.0)(3.00 x 10 8 m/s) = 6.00 x 10 7 m/s b) J is used, the SI definition includes kg so the mass must be converted to kg 9.109 x 10-8 g x kg/1000 g = 9.109 x 10-31 kg De Broglie equation: λ = Substitute in values: λ = h mv (6.63 x 10 34 J x s) 6.00 x 10 7 m x (9.109 x 10 s 31 kg) = 1.14 x 10-11 m x pm/10-1 m = 1.14 pm 3) Calculate the electron affinity enthalpy for Cl(g) given the following data: Enthalpy of formation, NaCl(s) = -41.0 kj/mol Enthalpy of sublimation, Na(s) = +108.4 kj/mol First ionization enthalpy, Na(g) = +495.7 kj/mol Bond dissociation enthalpy, Cl (g) = +43.3 kj/mol Lattice enthalpy, NaCl(s) = -779 kj/mol Formation reaction: Na(s) + ½ Cl (g) NaCl (s) Formation enthalpy = enthalpy of sodium sublimation + ionization enthalpy of sodium + bond dissociation of chlorine + electron affinity enthalpy of chlorine + lattice enthalpy Set up equation with x for value of electron affinity enthalpy for Cl(g) -41 kj = (1 mol Na(s))(108.4 kj/mol) + (1 mol Na(g))(495.7 kj/mol) + (1/ mole Cl )(43.3 kj/mol) + (1 mol Cl)(x kj/mol) + (1 mol NaCl(s))(-779 kj/mol) Solving for x: x = -367.8 kj 4) Calculate the molar enthalpy for the following reaction, given the table of bond enthalpies (in kj/mol). C=C 614 CΞC 839 C-O 358 C=N 615 CΞN 891 N=N 418 NΞN 941 O-H 467 CΞO 1074 O-O 146 O=O 495 C-C 347 C-N = 305 N-H 391 C=O 799 H-H 43 CO (g) + NH 3 (g) H O (g) + H N H N C=O Bonds broken: Bonds made: C=O ( mol)(799 kj/mol) = O-H ( mol)(467 kj/mol) = 6 N-H (6 mol)(391 kj/mol) = 4 N-H (4 mol)(391 kj/mol) = Sum 3944 kj C-N ( mol)(305 kj/mol) = Endothermic 1 C=O (1 mol)(799 kj/mol) = Sum 3907 kj Exothermic Bonds broken bonds made = 3944 3907 = 37 kj