Exam 1 Fall 2008-solutions

Exam 1 Fall 2008-solutions - Version 054 – Exam 1 Fall...

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Unformatted text preview: Version 054 – Exam 1 Fall 2008 – Brodbelt – (53765) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The use of programmable calculators, cell phones, or other electronic devices is prohib- ited. GOOD LUCK! 001 10.0 points Consider the following reaction: 2 FeS + 3 N 2 → 2 FeN + 2 SN 2 This reaction has a 65.0% yield. How much N 2 is consumed if 13.6 g of FeN are produced? 1. 0.190 mol 2. 31.4 mol 3. 0.150 mol 4. 412 mol 5. 0.449 mol correct 6. 0.899 mol 7. 0.200 mol Explanation: % yield = 65% m FeN = 13 . 6 g 13.6 g FeN is the actual yield. We need to first calculate the theoretical yield. % yield = actual yield theoretical yield theoretical yield = actual yield % yield ? mol N 2 = 13 . 6 g FeN × 100 65 × 1 mol FeN 69 . 86 g FeN × 3 mol N 2 2 mol FeN = 0 . 449 mol N 2 002 10.0 points The 23 Na + has eleven (11) protons, twelve (12) neutrons, and how many electrons? 1. 10 correct 2. 23 3. 11 4. 12 Explanation: Na has 11 e- ; Na + has one fewer e- for 10 total. 003 10.0 points All atoms of the same element always (even in chemical compounds) have the same 1. mass. 2. number of protons. correct 3. number of neutrons. 4. number of electrons. 5. The correct answer is not given. Explanation: The number of protons in an atom is char- acteristic of that atom, whether it is in its elemental state or if it is part of some com- pound. 004 10.0 points Different elements have different series of pho- tons that are absorbed or passed because 1. the photons are scattered off the nuclei. 2. the orbital energy levels differ. correct 3. they have a different number of protons. 4. photons have both wave-like and particle- like properties. 5. they have a different number of elec- trons. Explanation: 005 10.0 points p orbitals are shaped like dumbbells. They Version 054 – Exam 1 Fall 2008 – Brodbelt – (53765) 2 can have a principal quantum number of and they always have an angular mo- mentum quantum number of ....
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This note was uploaded on 07/27/2009 for the course CH 89959 taught by Professor Cowley during the Spring '09 term at University of Texas.

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Exam 1 Fall 2008-solutions - Version 054 – Exam 1 Fall...

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