MASC Solution to Midterm I Fall 2008

MASC Solution to Midterm I Fall 2008 - kJ/mole. The ionic...

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University of Southern California MASC 110L Midterm I E. Goo September 26, 2008 Answer all questions. All questions are of equal value. Must show your work neatly to get full credit. 1. Give the electronic configuration for the following atoms or ions: a) Si 1s 2 2s 2 2p 6 3s 2 3p 2 Or [Ne] 3s 2 3p 2 b) O 1s 2 2s 2 2p 4 Or [He] 2s 2 2p 4 c) Na + 1s 2 2s 2 2p 6 Or [Ne] d) Cl - 1s 2 2s 2 2p 6 3s 2 3p 6 Or [Ar] e) Ti 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 1s 2 2s 2 2p 6 3s 2 3p 6 3d 2 4s 2 is okay Or [Ar]4s 2 3d 2
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2. Give the steric number of the center atom and predict the shape of the following molecules a) CH 4 SN = 4 tetrahedral b) XeF 2 SN = 5 linear c) PCl 3 SN = 4 trigonal pyramidal , trigonal pyramid okay d) XeF 4 SN = 6 square, square planar okay e) PCl 5 SN = 5 trigonal bipyramidal, trigonal bipyramid okay
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3. Calculate the lattice energy of NaCl. The Madelung constant is 1.75. The ionization energy for Na is 496 kJ/mole and the electron affinity for Cl is -342
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Unformatted text preview: kJ/mole. The ionic radii for Na + is 102 pm and for Cl-is 181 pm. The distance is 283 pm ( )( ) mol kJ pm mol pm kJ x V / 491 283 1 1 10 389 . 1 5 − = − + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = The lattice energy is (1.75x-491) + 496 – 342 = -705 kJ/mole 4. A balloon is filled with hydrogen at 25 o C. If the balloon is cooled to 77 K what will be the percent change in the volume if the pressure is constant at two atm. From Charles Law the volume is proportional to the absolute temperature for a fixed amount of gas at constant pressure. The initial temperature is 298.15 K and the final temperature is 77K so the volume change in percent is: (298.15-77)/298.15 x 100% = 74.2 % decrease in volume...
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This note was uploaded on 02/13/2009 for the course MASC 110L taught by Professor Goo during the Fall '07 term at USC.

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MASC Solution to Midterm I Fall 2008 - kJ/mole. The ionic...

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