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Unformatted text preview: Su, Yung Exam 1 Due: Sep 21 2007, 4:00 pm Inst: FAKHREDDINE 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. Each question is worth as assigned. 001 (part 1 of 1) 8 points A pure substance composed of two or more elements chemically combined is 1. a mixture. 2. a compound. correct 3. an atom. 4. a solution. Explanation: A compound is a substance composed of two or more elements chemically combined. 002 (part 1 of 1) 8 points Which of the following types of electromag- netic radiation has the highest frequency as- sociated with it? 1. infra red 2. ultra violet 3. gamma correct 4. radio 5. x-rays Explanation: E = h f Gamma radiation has the highest energy of those listed and thus the highest frequency. 003 (part 1 of 1) 12 points Which of the following experiments most di- rectly supports de Broglies hypothesis of the wave nature of matter? 1. alpha-particle scattering by a metal foil 2. the photoelectric effect 3. the emission spectrum of the hydrogen atom 4. blackbody radiation 5. electron diffraction by a crystal correct Explanation: de Broglies hypothesis is that all matter possesses wave-like properties. Waves also exhibit a property known as diffraction. Elec- trons are often described as particles, but when a beam of electrons is aimed at a crys- tal, it undergoes diffraction. The resulting pattern varies depending on the exact crystal structure. The scattering experiment showed that most of the mass of an atom was con- centrated in a small, positive center which repelled alpha particles, but it did not pro- vide any further structural information on the metal foil. 004 (part 1 of 1) 12 points The atomic weight of a newly discovered el- ement is 110.352 amu. It has two naturally occuring isotopes. One has a mass of 111.624 amu. The other has an isotopic mass of 109.875 amu. What is the percent abundance of the last isotope (109.875 amu)? 1. 37.5% 2. 62.5% 3. 72.7% correct 4. 27.3% 5. 54.2% 6. 45.8% Explanation: Let x = the percent abundance of the last isotope. Then the percent abundance of the first isotope would be 1- x . Remember that x is the decimal form of the percent, and is Su, Yung Exam 1 Due: Sep 21 2007, 4:00 pm Inst: FAKHREDDINE 2 some fraction of 1. (109 . 875) x + (111 . 624)(1- x ) = 110 . 352 109 . 875 x + 111 . 624- 111 . 624 x = 110 . 352- 1 . 749 x =- 1 . 272 x = 0 . 727 = 72 . 7% 005 (part 1 of 1) 9 points Which set of quantum numbers does NOT provide a satisfactory solution to the wave equation?...
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