CH304K_HW05 - hyun (hh7953) Homework 5 Sparks (53435) 1...

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Unformatted text preview: hyun (hh7953) Homework 5 Sparks (53435) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points In the past hundred years, the atmospheric concentration of CO 2 has 1. gone up by about 200 percent. 2. gone down by about 20 percent. 3. gone up by about 20 percent. correct 4. gone up by about 80 percent. Explanation: 002 10.0 points Greenhouse gases 1. absorb dangerous ultraviolet radiation. 2. trap some of the heat energy Earth would otherwise radiate into space. correct 3. first appeared on Earth about the time of the industrial revolution. 4. can not absorb infrared radiation. 5. absorb all visible light. Explanation: 003 10.0 points Calculate the number of moles of Cl 2 molecules in a sample that contains 7 . 12 10 25 molecules of Cl 2 . 1. 1 . 40 10- 26 mol 2. 4 . 29 10 47 mol 3. 8 . 46 10- 3 mol 4. 1 . 18 10 2 mol correct Explanation: n Cl 2 = 7 . 2 10 25 molec We can use Avogadros number to convert molec of chlorine to moles chlorine: n Cl 2 = 7 . 12 10 25 molec Cl 2 1 mol Cl 2 6 . 022 10 23 molec Cl 2 = 118 . 233 mol Cl 2 004 10.0 points How many atoms are contained in 1 . 5 10- 2 moles of iron (atomic weight 55.85)? 1. ( 1 . 5 10- 2 )( 6 . 022 10 23 ) atoms cor- rect 2. ( 1 . 5 10- 2 ) (55 . 85) ( 6 . 022 10 23 ) atoms 3. Not determinable from the information given 4. ( 1 . 5 10- 2 ) (55.85) atoms 5. 6 . 022 10 23 atoms Explanation: n = 1 . 5 10- 2 mol There are Avogadros number of iron (Fe) atoms in one mole of Fe atoms. ? Fe atoms = 1 . 5 10- 2 mol Fe 6 . 02 10 23 atoms Fe 1 mol Fe = ( 1 . 5 10- 2 )( 6 . 022 10 23 ) 005 10.0 points How many electrons are in 1 mole of carbon atoms? 1. 6 2. 6 6 . 022 10 23 correct 3. depends on the isotope of carbon 4. 12 6 . 022 10 23 5. 12 hyun (hh7953) Homework 5 Sparks (53435) 2 Explanation: n C = 1 mol Each carbon atom has 6 electrons. One mole of carbon atoms has 6 . 022 10 23 carbon atoms. The number of electrons in one mole of carbon atoms: ? electrons = 1 mole C 6 . 022 10 23 C atoms 1 mole C 6 electrons C atom = 6 6 . 022 10 23 electrons 006 10.0 points One mole of H 2 contains (the same number of, more, fewer) atoms than/as one mole of He? 1. more correct 2. the same 3. fewer Explanation: One mole He atoms contains 6 . 02 10 23 He atoms. One mole of H 2 molecules contains 6 . 02 10 23 H 2 molecules. Since there are two H atoms for each H 2 molecule, there are ? H atoms = 6 . 02 10 23 H 2 molecules 2 H atoms 1 H 2 molecule = 1 . 204 10 24 H atoms. The H 2 sample has more atoms....
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CH304K_HW05 - hyun (hh7953) Homework 5 Sparks (53435) 1...

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