3313Ex1Sp02 - ~;~ c.7 TEST 1 ENSC 3313 Spring 2002 Answer alllO Questions 2 points Name each Actinium(Ac is Element#89 and is naturally occurring

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~ ;;~ c.7 ENSC 3313, Spring 2002 TEST 1 Name Answer alllO Questions. 2 points each. Actinium (Ac) is Element #89 and is naturally occurring, but was not discovered until the beginning of this century. The most stable isotope is Ac-227 which has a half-life of21.6 years. Please calculate the fraction of a 100 ~g sample that would remain after 10 years. A = Aoe-tlA A Ao In = -tl~ In(O.5) = -21.6 yr/A .==> A = 31.2 yr. -10/31.2 = O 7 25 =e - '- - What wavelength (maximum) would incident radiation need to promote electrons across a band gap of width 0.7 eV? Planck's constant is 0.662 x 10-33 J.s; 1 eV = 0.160 x 10-18J; the velocity of light is 0.299 x 109 ms-l. 2. L\E=~ A Substituting (0.7)(0.160 x 10-18) = (0.662XlO-33)(0.299XlO9) A A = ULJlm Deteffi1ine by calculation whether CsI could adopt an 8 fold coordination structure. (Draw a cube of side a, put the largest ion at the comers, the other at the center. ) The ionic radii are Cs = 0.170 nrn, I = 0.220 nrn. 3
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This note was uploaded on 01/10/2012 for the course ENSC 3313 taught by Professor Staff during the Fall '11 term at Oklahoma State.

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3313Ex1Sp02 - ~;~ c.7 TEST 1 ENSC 3313 Spring 2002 Answer alllO Questions 2 points Name each Actinium(Ac is Element#89 and is naturally occurring

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