2. Chem Final ANSWERS

2. Chem Final ANSWERS - 1. An element with two isotopes...

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1. An element with two isotopes (approximately 45% and 55% abundance) has a periodic table atomic mass of 161.71 u. One of the isotopes has a mass of 159 u. Which choice is most likely to be the mass number of the second isotope? Student Response Value Correct Answer Feedback A. 159 B. 157 C. 164 D. 158 E. 162 Score: 0/1 2. Consider the isotope bromine-81 ( 81 Br). Select the combination which lists the correct atomic number, number of neutrons, and mass number, respectively. Student Response Value Correct Answer Feedback A. 35, 46, 81 B. 35, 81, 46 C. 81, 46, 35 D. 46, 81, 35 E. none of these Score: 0/1
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3. What is the sum of the numbers of neutrons and electrons in the ion 72 As 3+ ? Student Response Value Correct Answer Answer: not answered 0% 69 Score: 0/1 4. In a hydrogen atom, from what energy level must an electron fall to the n = 3 level to give a line at 1.28 μm in the infrared region? Student Response Value Correct Answer Feedback A. 2 B. 4 C. 5 D. 6 E. 7 Score: 0/1 5. Which is not a possible m l value for an orbital that has the following: l = 3 Student Response Value Correct Answer Feedback A. +4 B. –2 C. –1 D. –3 Score: 0/1
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6 . Give formulas for the following compounds: chlorine trifluoride and pentaphosphorus heptasulfide Student Response Value Correct Answer Feedback A. ClF 3 , 5PS 7 B. ClF 3 , P 5 S 7 C. Cl 3 F, P 3 S 9 D. Cl 3 F 3 , P 5 S 7 E. ClF 3 , PO 5 S 7 Score: 0/1 7 . How many molecules of H 2 O are present in 808.8 g of H 2 O? Express your answer in scientific notation (i.e., 1.23 x 10 4 = 1.23E4) with three significant figures. Student Response Value Correct Answer Answer: not answered 0% 2.70E25 (2.70 × 10 25 ) Score: 0/1
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8 . Choose the correct Lewis electron-dot symbol for the atom below. Se Student Response Value Correct Answer Feedback A. B. C. D. E. none of these Score: 0/1
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9 . What stable monatomic ions do rubidium (Z = 37) and selenium (Z = 34) form? Student Response Value Correct Answer Feedback A. Rb 2- and Se 2+ B. Rb + and Se 2- C. Rb + and Se 2+ D. Rb - and Se 2- E. Rb + but Se does not form a stable ion. Score:
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2. Chem Final ANSWERS - 1. An element with two isotopes...

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