homework_5_answers - Grodin, Micah Homework 5 Due: Oct 11...

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Unformatted text preview: Grodin, Micah Homework 5 Due: Oct 11 2005, 11:00 pm Inst: Sara Sutcliffe This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Name the compound NiO. 1. nickel oxygenate 2. nickel monoxide 3. nickel(I) oxide 4. nickel oxide 5. nickel(II) oxide correct Explanation: 002 (part 1 of 1) 10 points Choose that pair of names and formulas that do not match. 1. Fe2 (SO4 )3 : iron(III) sulfate 2. MnCO3 : manganese(II) carbonate 3. SnO : tin(II) oxide 4. SnCl4 : tin(IV) chloride 5. Cu2 O : copper(II) oxide correct Explanation: The copper(II) ion is Cu2+ ; the oxide ion is O2- . One O2- is needed to balance the charge of each Cu2+ , so the correct formula for copper(II) oxide is CuO. In Cu2 O, the total charge from copper ions must be +2 to balance the -2 charge from the oxide ion. Each copper ion would have a charge of +1. This compound is copper(I) oxide. The manganese(II) ion is Mn2+ ; the carbonate ion is CO3 2- . One CO3 2- is needed to balance the charge of each Mn2+ , so the formula is MnCO3 . The tin(IV) ion is Sn4+ ; the chloride ion 1. chlorine 2. oxygen 3. fluorine 4. sodium correct 1 is Cl- . Four Cl- are needed to balance the charge of each Sn4+ , so the formula is SnCl4 . The tin(II) ion is Sn2+ ; the oxide ion is O2- . One O2- is needed to balance the charge of each Sn2+ , so the formula is SnO. The iron(III) ion is Fe3+ ; the sulfate ion is SO4 2- . Three SO4 2- are needed to balance the charge of every two Fe3+ . (This gives a total anion charge of -6 and a total cation charge of +6.) The formula is Fe2 (SO4 )3 . 003 (part 1 of 1) 10 points How many sodium atoms are in one formula unit of sodium nitrate? 1. 5 atoms 2. 2 atoms 3. 3 atoms 4. 4 atoms 5. 1 atom correct Explanation: The sodium ion is Na+ and the nitrate ion is NO- . One NO- is needed to balance the 3 3 charge on each Na+ . The formula is NaNO3 . 004 (part 1 of 1) 10 points Which one of the following has the LOWEST electronegativity? Explanation: Electronegativity is the measure of an element's tendency to attract electrons to itself when it is combined with another atom. This depends first of all on whether the element wants to gain electrons or lose them in order to have a stable configuration (think octet rule and noble gases). Elements on the right- Grodin, Micah Homework 5 Due: Oct 11 2005, 11:00 pm Inst: Sara Sutcliffe ! 2 S ! ! ! 1. increases, then decreases. 7. Na + S 5 55 55 4 2. decreases, then increases. 3. decreases. correct - S S - DD A A A 6 6 AA 66 66 Na+ + 8. Na + B B - S + S F FF F 9 9. Na + E - G G Na 006 (part 1 of 1) 10 points Use electron-dot notation to demonstrate the formation of an ionic compound involving the elements Na and S. 1. Na + + S 10. None of these Explanation: Na gives up an electron to form the Na I 4. Na + Na + S - Na +Na + S + S + S 3+ 3+ 2- 2- 2- Na2 S3 3. Na + Na + S + S + S - - 007 (part 1 of 1) 10 points When a fluorine atom reacts with a chlorine atom, the bond that forms between them should be 1. ionic-covalent. 2. polar covalent. correct T T T T Na + Na + S T T Na + S - NaS + + T T 3+ 3- S Na + Na + S SS SS R Q 2. Na + S - S P P form the S PP P 7P PP Na + S + S 2+ - - cation and - NaS2 S 2- II I S II + S - acquires two electrons to anion: - 2- GG GG 2+ G G D D C C FF E Explanation: Electronegativity generally increases from left to right and from bottom to top of the Periodic Table. Na + S S + DD CC CC BB BB 3+ - - S D D C C B B 5. stays the same. @ + S + 2- AA @@ @ @ @@ 99 9 9 99 8 8 4. increases. 8 - - Na2 S3 3 3 6 76 2 2 Na + Na + Na + S + S - NaS - NaS - Na2 S 33 33 22 22 2+ 2+ 2+ 3- 3- Na3 S2 1 1 3 3 0 0 2 2 ) 5 5 ( ' 005 (part 1 of 1) 10 points Moving down a column in the periodic table, the electronegativity generally 6. Na + Na + Na + S + S 11 1 00 0 & & Na + Na + Na + ) ( ' S && && + + + 3- % % 5. Na + Na + Na + & & S %% % $ ! ! # " hand side of the periodic table form negative ions and want more electrons while elements on the left-hand side form positive ions and want to lose electrons. Electronegativity decreases going down a column and increases going to the right across a row. Flourine is the most electronegative element. Na+ + Na+ + ! ! 2- - Na2 S correct - - Na3 S - - + H Grodin, Micah Homework 5 Due: Oct 11 2005, 11:00 pm Inst: Sara Sutcliffe Cl Cl Cl i i i `i i h h 3 3. ionic. 9. 4. nonpolar covalent. Explanation: 10. i Cl N 1. Cl U U N U Cl U Cl U U V WV Explanation: N = 5 valence e- Cl = 3 7 valence e- Total = 26 valence e- . Cl p p p `p p V V 7. Cl e e Cl N f f t H t t t t t 5. t t t g g gg Cl Cl H C O t g g 8. t t t `t Cl N d d Cl d 3. Cl 4. H H C H O C H s O s s s d d d b `b b b 6. Cl N r r c Cl r H r r r c a Cl c c a a a 2. H C q q 5. Cl a N a Cl q H q O q q 1. q H q C q O q q q Y Cl Y Y a Wa Y Y Y Y Y Y `Y 4. Y Cl Y N Cl Y Y Y X Cl X X Y WY X X X 3. X Cl X N X Cl satisfies the octet rule for each atom and there are a total of 26 valence e- . 009 (part 1 of 1) 10 points Which of the following is the correct Lewis formula for formaldehyde (CH2 O)? correct correct p Cl p p p p p X X X V Cl V V V p N Cl p p V V 2. p p p `p p `p Cl V N V Cl i Cl i i i N i Cl i i i 008 (part 1 of 1) 10 points Which of the following is the correct Lewis formula for nitrogen trichloride (NCl3 )? i i h h i `i V V Y `Y b `b Y Grodin, Micah Homework 5 Due: Oct 11 2005, 11:00 pm Inst: Sara Sutcliffe resonance: O u u u Wu 4 6. H u u C H C v u u v Wv O S O O 2- H v v v Explanation: The Lewis formula O H (CH2 O) is H C 2. CO2- 3 3. SO3 4. NO- 3 5. SO2- correct 3 Explanation: There is only one Lewis structure that can be drawn for SO2- , so it does not exhibit 3 SF6 has 48 e- but S has an expanded valence shell containing 12 e- , thus violating the octet rule. 012 (part 1 of 1) 10 points By what could a 300 nm photon be absorbed? 1. O3 but not O2 correct 2. O2 but not O3 F F W 1. All of the other answers have ions or molecules which exhibit resonance. F S F W F F 010 (part 1 of 1) 10 points Which of the following does NOT exhibit resonance? H ` 10. H C O H ` ` 9. H C O y y y y H H yy 8. O C v v x x v v w w v `v ` 7. v H v O satisfies the octet rule for each atom and has 26 e- . All of the other molecules listed here can have at least two correct but different Lewis structures drawn for them. Calculate (S/2)/B; if you get a fraction greater than one, that molecule exhibits resonance. The Lewis dot structure for SO3 contains O single bonds and 1 S O double 2S bond. You can draw three different structures for SO3 . Also, (S/2)/B = (4/2)/3 = 2/3 = 0.66; fractions indicate resonance or delocalization of electrons. 011 (part 1 of 1) 10 points Which one of the following compounds does NOT obey the octet rule? 1. H2 O 2. SF6 correct for formaldehyde 3. NH3 4. CH4 Explanation: S has 6 valence e- F has 6 7 valence e- Total = 48 valence e- v v v v `v v Grodin, Micah Homework 5 Due: Oct 11 2005, 11:00 pm Inst: Sara Sutcliffe 4. I and III only correct 3. either O2 or O3 5. II only 4. neither O2 nor O3 Explanation: 013 (part 1 of 1) 10 points Which has the shortest wavelength? 1. UV-C correct 2. UV-B 3. UV-A 4. All have equal wavelengths Explanation: UV-C is the most energetic and therefore the most dangerous to humans; it is completely absorbed by stratospheric ozone and oxygen. UV-B is less energetic and not quite as dangerous; it is partially absorbed by stratospheric ozone. UV-A is the least energetic and least dangerous; it is not absorbed by the atmosphere. High energy waves have higher frequencies and shorter wavelengths; low energy waves have lower frequencies and longer wavelengths. 014 (part 1 of 1) 10 points Which of I) Ozone reacts with oxygen atoms to form oxygen molecules; II) Ozone is removed by its reaction with water vapor; III) Ozone is removed by an interaction with UV radiation causing it to dissociate into an oxygen molecule and an oxygen atom. is/are part(s) of the Chapman cycle in the stratosphere? 1. I only 2. None of these 3. I and II only 6. All of these 7. II and III only 8. III only Explanation: 5 015 (part 1 of 1) 10 points Lewis dot structures provide a simple rationalization for the fact that O3 absorbs light of larger wavelengths than O2 . The rationalization is that 1. O3 is a radical. 2. resonance structures show that O3 has one and a half bonds between each pair of atoms whereas O2 is double bonded. correct 3. O3 is found higher up in the atmosphere where there is more UV light. 4. O3 is a cyclic molecule. 5. O3 vibrational frequencies are lower, making it easier to dissociate the molecule with light. Explanation: ...
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This homework help was uploaded on 04/07/2008 for the course CH 304k/305k taught by Professor Sutcliffe during the Fall '05 term at University of Texas.

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