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classes_Winter08_14A-1ID1_Midterm_solutions_14A-1_BLUE

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Unformatted text preview: C' (3 L m. : Chemistry l4A-1d Midterm #1, February 13, 2008 Instructor: Dr. Ross Larsen ' A k) 5 [k/ 2: 92 ngv Name (print clearly) Student ID Instructions and hints: Read all questions before beginning work. Show all your work. If you need more space, use the back of the page, but indicate clearly where your work can be found. To ensure your answer is graded, circle your final answer. Be careful about units and significant figures! A periodic table and other possibly useful information may be found at the back of this test. I certify that the work on this examination is entirely my own and that I have read and understood the above rules, as well as the grading and cheating policies described in the course syllabus (test will not be graded unless signed). Signature _ Problem _— Points possible Points 1 20 _ 2 20 _ 3 20 __ 4 20 __ Total 80 (l, 1 "A” (20 pts) Draw Lewis dot diagrams for the following molecules, including determining the formal charge on each atom. Where multiple diagrams are possible, include all possible Lewis dot structures and determine which one(s) will be most stable. a) (8 pts) Nitryl chloride (ClNOz) (N is the central atom) i. 33 ’ , / i ‘ w, \J’ ; (a \ ) -. , f ‘9.) \ f, I/\’ [in-H mr’ (“fuel/5 {limb/<3 b) (6 pts) 2,2,2 trichloroethanol (CCl3CH20H). The chlorines are attached to one carbon, the, carbons to each other, and the 2 hydrogens and the OH to the other carbon. al- I i ) (l " C-~~-C<—~— OM H , I i w ‘ s (it Kl "/ fg/(continued) c) (6 pts) Using the VSEPR model, give the steric number, name the molecular shape, and estimate the indicated bond angles of PCl3(drawn below). \le <49 (20 pts) Light is shined on a metal with work function 4.14 x 10-19 J. a) (10 pts) What is the largest wavelength of light that will eject electrons from the metal (in m)? /“‘ “ . 7 IL/ 11': ’3 m ,‘r‘, H’Y‘iu {In ”([317 le/hflj " \/ : “J i [q C l-W C. l »« wit» \ «V. , xx: , at i h t ”A” '7wa J b) (10 pts) If the same metal as in part (a) has light of frequency V = 7.13 X 1014 s‘1 shined on it, what is the kinetic energy of the electrons ejected from the metal (in J)? What is the wavelength (in nm)? Liv : (iv/Cl : l» ( '%13xloii’<7 ’ 777 Xlo ‘5 / - 3 Q _ 2". / W V ('7',(o"ix13372?7{flat/‘0?" " 7 X N I ( *‘ 5 “/34 (20 pts) The solid fuel in the booster stage of the space shuttle is a mixture of ammonium perchlorate and aluminum powder. On ignition, the reaction that takes place is 6 NH4ClO4(s) + 10 Al(s) -> 5A1203(s) + 3N2(g) + 6 HCl(g) + 9 H20(g). a) What mass of aluminum should be mixed with 1.325 kg of NH4ClO4 for this reaction? _ . 5 “l wi 159,154,933 15 ill-(.331 4 35ft53 4 L15 Igflznt, )‘j/mol 1" H7 {53‘ “Ml r ,5 (I i 5:555 M 5 "3 ”3‘ ‘° J. II. 15 5 m, C) o ”3,5555m “' j; ,1 ”,1g hag’t’rj :: I?! g'o Mg’fflfi 0“, A) ‘ W l 25.7555 / (m an, ty- : om 92/ ”'7’ b) Determine the mass of A1203 (alumina, a finely divided white powder that is produced as billows of white smoke) formed in the reaction of 3.500 X 103 kg of aluminum. 3.500113gi 5 Q ,7 4 5 of A/ :j :' [‘l‘ll x to 5555‘ ).)W K Id ’27 3.12135571th A’ f 15.435foqu 5551‘ A] 0 L L \g (20pts) For the following atoms or ions, draw and label orbital diagrams (energy-level diagrams), including all orbitals up to n=3. Using the Pauli exclusion principle and Hund's rules, indicate which orbitals are occupied and the spin of each electron. Write the electronic configuration of the atom (use the [Noble gas configuration] notation if you wish). (Don't forget to label the direction of increasing energy.) a) (6pts) H \ s ‘ ~... ._..—— W J ( rt 5/: X f‘) _ F Ez/i r“ W .. z"; ~— - W 4N i’l‘ 315» (aw/j #3 [We SAW 1' J g :‘r x . ,~ 1 {(7 Ll \ \. fl (continued) c) (6pts) Give all possible quantum numbers n, l,m for the 25 and 4p orbitals. ...
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