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ch304k_exam3_solution_pdf

ch304k_exam3_solution_pdf - Version 028 Exam 3 Sparks(53435...

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Version 028 – Exam 3 – Sparks – (53435) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Which one has the greatest mass? 1. 3.1 moles of O atoms correct 2. 3 . 2 × 10 3 kg of O 2 molec 3. 3.2 g of O atoms 4. 4 . 23 × 10 23 O 2 molec Explanation: Convert all to g or kg and compare: For 3 . 2 × 10 3 kg O 2 : 3 . 2 × 10 3 kg O 2 × 1000 g 1 kg = 3 . 2 g For 3.2 g O: 3.2 g For 3.1 mol O: 3 . 1 mol O × 16 g 1 mol O = 49 . 6 g For 4 . 23 × 10 23 molec O 2 : 4 . 23 × 10 23 O 2 molec × 1 mol O 2 mol 6 . 022 × 10 23 O 2 molec × 32 g 1 mol O 2 = 22 . 5 g 3.1 moles of O atoms has the greatest mass. 002 10.0 points We obtain evidence about past carbon dioxide concentrations in earth’s atmosphere by 1. analyzing the concentration of carbon dioxide in air bubbles in ice core samples. correct 2. the 2 H to 1 H ratio in ice core samples. 3. the 14 C to 12 C ratio in microorganisms found in ice core samples. 4. the 14 C to 12 C ratio in our current atmo- sphere. Explanation: 003 10.0 points What is the molecular geometry around oxy- gen in the molecule CH 3 CH 2 OH ? 1. square planar 2. trigonal planar 3. bent correct 4. linear 5. tetrahedral 6. trigonal pyramidal Explanation: 004 10.0 points If the concentration of carbon dioxide in the atmosphere increased dramatically, which would you expect? Choose the best answer. 1. decreased temperatures 2. increased temperatures correct 3. decreased temperatures and increased in- cidence of skin cancer 4. decreased temperatures and decreased in- cidence of skin cancer 5. increased temperatures and decreased in- cidence of skin cancer 6. decreased incidence of skin cancer 7. increased temperatures and increased in- cidence of skin cancer 8. increased incidence of skin cancer Explanation: CO 2 is a greenhouse gas and absorbs IR photons. The molecule vibrates in response to the IR absorption, which increases the tem- perature of the atmosphere. Incidence of skin
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Version 028 – Exam 3 – Sparks – (53435) 2 cancer is dependent on the condition of the ozone layer, which is dependent on CFCs, free radicals, and UV absorption, not greenhouse gases nor global warming. 005 10.0 points Greenhouse gases absorb (IR, microwave, UV, visible) radiation; ozone absorbs (IR, UV, vis- ible) radiation. 1. IR radiation; UV radiation correct 2. UV radiation; IR radiation 3. UV radiation; UV radiation 4. IR radiation; IR radiation 5. visible radiation; visible radiation 6. microwave radiation; UV radiation Explanation: 006 10.0 points If a molecule of AB 2 has two lone pairs of electrons on A, what would you estimate the B-A-B bond angle to be? 1. around 90 degrees 2. around 45 degrees 3. around 120 degrees 4. around 10 degrees 5. around 62.5 degrees 6. around 109.5 degrees correct 7. around 360 degrees 8. around 180 degrees Explanation: A B B or A B B has 4 RHED with a tetrahedral electronic geometry and trigonal pyramidal molecular geometry. The lone pairs will distort the 109.5 bond angles slightly.
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