REV09

# REV09 - CHM 115 Review Final Exam May 4th 2009 Elliot Hall...

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CHM 115 Review Final Exam: May 4th 2009 Elliot Hall of Music 1:00 pm 35 Questions, 210 points 2 Hours Be there!

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Think/Pair/Share Question #1 How many nucleons are in a 19 F nucleus? (Answer with a number.) 9 Mass number, # of protons + neutrons = # of nucleons Symbol Atomic number, number of protons 19 F 9
Types of Radioactive Decay a helium nucleus , an electron , a photon, no charge, no mass e -1 0 +2 4 He Some elements undergo spontaneous decay to form more stable elements γ α β

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98 98 229m Th 90 229 Th 90 212 Po 84 208 Pb 82 Tc 43 Ru 44 a. b. c. Question #2 Which change involves alpha-decay ? (unstable nucleus to stable nucleus)
Which change involves alpha-decay ? Tc 43 Ru 44 a. 229m Th 90 229 Th 90 b. 212 Po 84 208 Pb 82 c. Nuclear equations 98 98 + e -1 0 + He 4 +2 + Σ reactant atomic numbers = Σ product atomic numbers Σ reactant mass numbers = Σ product mass numbers γ 0 0

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Question #3 Σ reactant atomic numbers (charge) = Σ product atomic numbers (charge) Σ reactant mass numbers = Σ product mass numbers Identify the atomic number of X. 25 12 Mg + 4 2 He A Z X + 1 1 H
Mass defect Mass of nucleus is not equal to the sum of the masses of individual nucleons in the nucleus. 14 7 N 7 1 1 H + 7 1 0 n 14.0031 amu 14.11543 amu The 14 7 N nucleus is missing 0.1123 amu. This is the mass defect.

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E = mc 2 or E = mc 2 E = energy (in J) produced when mass m is converted into energy or consumed when energy is converted to mass m = mass in kg (1 amu = 1.6605 x 10 –27 kg) c = speed of light (2.9978 x 10 8 m s -1 ) 14 7 N 7 1 1 H + 7 1 0 n E = N. B. E. N. B. E. = Energy required to separate nucleus of atom into protons and neutrons.
Question # 4 a. 1.0 x 10 16 J b. 3.4 x 10 7 J c. 1.7 x 10 -11 J d. 5.6 x 10 -20 J What is the N. B. E of 14 7 N per nucleus? 14 7 N 7 1 1 H + 7 1 0 n E = N. B. E. m = 0.1123 amu 1 amu = 1.66 x 10 –27 kg c = 3.00 x 10 8 m s -1

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Question # 4 a. 1.0 x 10 16 J b. 3.4 x 10 7 J c. 1.7 x 10 -11 J d. 5.6 x 10 -20 J What is the N. B. E of 14 7 N per nucleus? 14 7 N 7 1 1 H + 7 1 0 n ΔE = N. B. E. m = 0.1134 amu 1 amu = 1.66 x 10 –27 kg c = 3.00 x 10 8 m s -1 m = 0.1123 amu x 1.66 x 10 -27 kg/1 amu = 1.86 x 10 -28 kg E = 1.86 x 10 -28 kg x (3.00 x 10 8 m s -1 ) 2 = 1.67 x 10 -11 kg m 2 s -2 = 1.67 x 10 -11 J N.B.E. = 1.7 x 10 -11 J/nucleus
First order radioactive decay 6 h 6 h 6 h 6 h t 1/2 = 6 h

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Pu-239 half-life is 24,000 years. How much plutonium-239 remains in a sample that initially contained 1.0 kg of plutonium after 96,000 years? a. 1/2 kg b. 1/4 kg c. 1/8 kg d. 1/16 kg Question #5
Example How long will a cobalt–60 source be useful if it can be used until the gamma rays it produces reach 70 percent of the original intensity? 60

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## This note was uploaded on 02/06/2012 for the course CHM 115 taught by Professor Towns during the Spring '08 term at Purdue.

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REV09 - CHM 115 Review Final Exam May 4th 2009 Elliot Hall...

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