hw 1 - Garg Pallavi – Homework 1 – Due 11:00 pm –...

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Unformatted text preview: Garg, Pallavi – Homework 1 – Due: Sep 18 2007, 11:00 pm – Inst: Donna C Lyon 1 This print-out should have 36 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. This HW assignment is due Monday, September 17 by 11:00PM. 001 (part 1 of 1) 10 points Which of the following species has the greatest number of electrons? 1. Ca 2+ 2. Cu 2+ correct 3. Ti 2- 4. Ni 3+ 5. Mn Explanation: A positively charged ion has lost electrons while a negatively charged ion has gained elec- trons. Ni 3+ has 25 electrons Mn has 25 electrons Ti 2- has 24 electrons Cu 2+ has 27 electrons Ca 2+ has 18 electrons 002 (part 1 of 1) 10 points The number of protons in a chloride ion (Cl- ) is 1. 16. 2. 17. correct 3. 35. 4. 18. Explanation: 003 (part 1 of 1) 10 points The number of electrons in a sulfide ion (S 2- ) is 1. 18. correct 2. 14. 3. 32. 4. 16. Explanation: 004 (part 1 of 1) 10 points The atomic weight of a newly discovered el- ement is 10.600 amu. It has two naturally occuring isotopes. One has a mass of 10.000 and a natural abundance of 70.000%. What is the isotopic mass of the other isotope? 1. 11.200 2. 12.000 correct 3. 10.500 4. 11.000 5. 11.500 6. 9.5000 7. 10.000 8. 9.0000 9. 10.600 Explanation: The atomic weight equals the sum of the isotopic masses times their natural abun- dance. We know one isotope’s natural abun- dance is 70%, so the other must make up 30%. Let x equal the unknown mass. (10 . 000)(0 . 70) + ( x )(0 . 30) = 10 . 600 7 . 0000 + 0 . 30 x = 10 . 600 . 30 x = 3 . 6000 x = 12 . 000 Garg, Pallavi – Homework 1 – Due: Sep 18 2007, 11:00 pm – Inst: Donna C Lyon 2 005 (part 1 of 1) 10 points Write the nuclear symbol for oxygen-16. 1. O 8 16 2. 8 O 8 3. 8 O 8 4. 8 O 8 5. 16 8 O correct 6. 8 16 O 7. 8 8 O 8. O 8 8 9. 8 O 8 10. O 16 8 Explanation: nuclear symbol for oxygen-16 = ? For oxygen-16 (element O), atomic number = 8 (located at lower left of symbol) mass number for oxygen-16 = 16 (located at upper left of symbol) oxygen-16: 16 8 O 006 (part 1 of 1) 10 points The isotope 206 82 Pb has 1. 206 neutrons. 2. 124 neutrons. correct 3. 206 protons. 4. 82 neutrons. Explanation: For A Z X , A = mass number = # p + + # n and Z = atomic number = # p + . 206 82 C has 82 protons, so it has 206- 82 = 124 neutrons. It is neutral, so # e- = # p + = 82 . 007 (part 1 of 1) 10 points The number of neutrons in 13 C is 1. 13. 2. 8. 3. 10. 4. 7. correct 5. 6. Explanation: The number in the upper left-hand corner to an element’s symbol is the mass number of this particular isotope. The mass number is simply the sum of the number of protons (which is fixed) and neutrons (which varies, identifying individual isotopes). Since C has 6 protons (all C atoms contain 6 protons), there must be 7 neutrons to account for a mass number of 13....
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This note was uploaded on 09/17/2009 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas.

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hw 1 - Garg Pallavi – Homework 1 – Due 11:00 pm –...

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