chem exam final - FINAL EXAM NAME Chemistry 030.204 Last,...

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Unformatted text preview: FINAL EXAM NAME Chemistry 030.204 Last, First Dr. K. H. Bowen Friday, May 9, 2003 SSN Instructions: Write your name and social security number in the blanks provided above. There are 5 problems/questions on this exam. Please answer all of them. Percentage credit is indicated for each. Please confirm, before you begin, that your copy of this exam contains all five problems/questions plus a periodic table. This is a closed book, closed notes exam. The use of calculators is not allowed. Show all of your work and reasoning on the pages provided. Problem Number Valuegljof problem (in points) Number of points actually earned #1 25 #2 10 #3 25 #4 20 #5 20 5 problems 100 total pts. possible TOTAL SCORE = Problem #1 Chemical Kinetics (25 points total) (a) [20 points] Define or describe the meaning of the following terms. (i) Lindemann mechanism ’1’ (ii) Expression showing hon} rate constants are related to temperature. Name this expression. %=/4€"EMVV#Q/4wmw (iii) Law of Mass 111:3?“ 0% Q d; E 4%? #Q' finj’l: ‘9; 7w» pref: v ’ ‘7 ' , EX, A+zflffiffws=t> “my “ ACNE/g] (iv) teady—State Approximation eféi" ngm; finoé‘mof‘mw @‘M" fiv/“ngswafiwafw7é WW. (v) Principle of Microscopic Reversibility r e WWMWAQM s fiwwiwmjflt M Maggi—:5 @aim'mwi ‘ E (b) [5 points] Suppose that two, continuously—operating molecular beams, one of reactant molecule, A, and the other of reactant molecule, B, cross at 90° in a high vacuum chamber to yield product molecules, C and D. How many @131 product molecules are produced per second? You will find the following information useful in solving this problem. Each reactant beam is traveling at a velocity of 400 m/sec. The intensity of each beam is 1018 molecules/cmz'sec. The interaction volume where the two beams overlap can be approximated as a cube, 0.1 cm on each side. The reactive cross section for the reaction, A + B -) C + D is 10 AZ. Show all of your work in detail. If square roots appear in this 8problem, you do not need to evaluate them. Do everything in units of cm and sec. (1A = 10‘ cm) Problem #1 (continued) mam/Flt"; - (a, “z ‘1 Par (MXID’WAs‘X/ouj’mMagma" 1W5 W 3 «I .. ré.2§Xt/§szo°xw' ’JBflL My Recall the story of The Three Little Pigs, in which one little piggy built his/her house out of straw and paper, another piggy built his/her house out of wood and drywall, and still the other little piggy built his/her out of brick and steel plate. In each case, these houses provided significant protection from some form or forms of ionizing radiation. In the case of each house, list the types of ionizing radiation against which that house would protect its occupants. Problem #2 Nuclear Chemistry (10 pts.) 1 KEY Contrast and compare the following simple quantum mechanical systems side—by—side: 1—D particle in a box, rigid rotor, 1—D harmonic oscillator, and hydrogen atom. In each case, identify the kind of motion for which these systems are often used as models, write their energy expressions in terms of appropriate quantum numbers, sketch the potential, if there is one, draw in the first three energy levels, showing how their energy spacings change with increasing energy (stay the same, increase , or decrease?) label the quantum numbers of the first three levels, draw the wavefunctions for the first three energy levels in the cases of the particle in a box and the harmonic oscillator, indicate the zero point energy if there is one, and list the selection rules for the rigid rotor and the harmonic oscillator Problem #3 Simple Quantum Mechanical Systems (25 points) E (1) Which of the following molecules exhibit microwave absorption spectra, H2, NaCl, C12, HF, 02? [You must get all of these correct in order to receive any credit for this sub—problem] race) //F (2) What was the Stern—Gerlach experiment? What was its significance? P Ade-“w 42:: MW - Win (3) How many normal modes of vibration does 2S have? Wh ? ’3“ . 3’ M #20. 3mv'6 ‘4 7‘5 ‘3 (4) The molecular anion, XeO‘ is stable. structure. Problem #4 Questionson Spectroscopy and Bonding (20 points) Explain why in terms of periodicity and electronic X3024! MW WW 6&0) (5) Use VSEPR theory to determine the structure of PH3. ' — -~ . ~ gy=3+IW=§L rm 11% W W x x W 1+4 ‘H M m (byte 2%- (6) What is thdfionization energ y of the hydrogen atom in units of e ? [3. 66V (7) A spectral absorption in the visible or ultraviolet portion of the electromagnetic spectrum is exciting what kind of motion in the molecule being excited? W A”; 69;“ (8) A roximately, how many cm‘1 (wave~numbers) are there per eV (electron—volt)? PP N 970M Mer (9) In a diatomic molecule, by how much does D0 differ from De? De 5' Do 7L 5% (10) Which of the following molecules have non-zero dipole moments: HZS, NH3, benzene, C02? You must get all of these correct in order to receive any credit for this sub—problem. mg) m KEV Problem #5 Solids, Spectroscopy, Bonding, and Quantum Mechanics (20 points) A large number of molecules originally from a piece of an insulator form a finite size aggregate or cluster which has many of the same qualitative electronic properties as did the original insulator. An excess electron then attaches itself to the isolated cluster to make it become a negative cluster ion. At low temperature, what should one expect, in general terms, the electron affinity of this cluster to be equal to? Remember that insulators and semiconductors are each made up of a valence band, an energy gap, a conduction band, and a vacuum level. ...
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chem exam final - FINAL EXAM NAME Chemistry 030.204 Last,...

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