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Chapter 2 Atoms, Molecules, and Ions

Chapter 2 Atoms, Molecules, and Ions. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten. Troy Wood University of Buffalo Buffalo, NY  2006, Prentice Hall. How many neutrons are there in an atom of 14 C?. 6 8 12 14.

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Chapter 2 Atoms, Molecules, and Ions

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  1. Chapter 2Atoms, Molecules,and Ions Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Troy Wood University of Buffalo Buffalo, NY  2006, Prentice Hall

  2. How many neutrons are there in an atom of 14C? 6 8 12 14

  3. Correct Answer: 6 8 12 14 14 Mass number C 6 Atomic number The difference between the mass number and the atomic number is the number of neutrons (14  6) = 8.

  4. An isotope of Cr3+ ion containing 24 protons and 27 neutrons would contain ___ electrons. 21 24 27 3

  5. Correct Answer: 21 24 27 3 The +3 charge indicates there are 3 more protons than electrons: 24 3 = 21

  6. A hypothetical element has two isotopes. One of the isotopes has an abundance of 75.0% and a relative mass of 12.0 amu, while the other has an abundance of 25.0% and a relative mass of 14.0 amu. The atomic mass of this hypothetical element is 12.5 amu. 13.0 amu. 13.5 amu. 13.8 amu.

  7. Correct Answer: 12.5 amu. 13.0 amu. 13.5 amu. 13.8 amu. Atomic mass = (0.750)(12.0 amu) + (0.250)(14.0 amu) Atomic mass = 9.0 amu + 3.5 amu = 12.5 amu

  8. Chlorine has two isotopes, 35Cl (75.78% abundant) and 37Cl (24.22% abundant). How many different molar masses are possible for a Cl2 molecule? 2 3 4 5

  9. Correct Answer: 2 3 4 5 35Cl2 = 70 amu 35Cl37Cl = 72 amu 37Cl2 = 74 amu

  10. Which of the following species has the greatest number of electrons? • Cl • Ca2+ • P3 • K • Ar

  11. Correct Answer: • Cl • Ca2+ • P3 • K • Ar K has 19 electrons; all the other species listed have only 18 electrons.

  12. The compound, CuSO4, is called Calcium sulfide Carbon sulfide Calcium sulfite Calcium sulfate Copper sulfate

  13. Correct Answer: Calcium sulfide Carbon sulfide Calcium sulfite Calcium sulfate Copper sulfate The compound is ionic, derived from the copper(II) cation (Cu2+) and the sulfate anion (SO42).

  14. The correct name for the compound, MgC2 is Carbon magneside Magnesium carbide Magnesium carbonate Manganese dicarbide Magnesium dicarbide

  15. Correct Answer: Carbon magneside Magnesium carbide Magnesium carbonate Manganese dicarbide Magnesium dicarbide In this unusual ionic compound, the cation is magnesium cation (Mg2+) and the anion is carbide or acetylide (C22).

  16. The simplest chemical formula for the binary ionic compound CaxNy is Ca2N Ca2N3 Ca3N2 Ca3N

  17. Correct Answer: Ca2N Ca2N3 Ca3N2 Ca3N Ca loses two electrons to become Ca2+, while N gains three electrons to become N3. To be neutral, positive charges and negative charges have to balance.

  18. The ion Cr2O72 is known as: Chromos Chromite Chromate Dichromate Bichromite

  19. Correct Answer: Chromos Chromite Chromate Dichromate Bichromite Dichromate solutions are a deep orange color.

  20. The acid HClO3 is known as: Perchloric acid Chloric acid Chlorous acid Hypochlorous acid Hydrochloric acid

  21. Correct Answer: Perchloric acid Chloric acid Chlorous acid Hypochlorous acid Hydrochloric acid

  22. The molecular compound N2O4 is named: Nitrogen oxide Oxygen nitride Dinitrogen quartoxide Dinitrogen tetroxide Nitrous oxide

  23. Correct Answer: Nitrogen oxide Oxygen nitride Dinitrogen quartoxide Dinitrogen tetroxide Nitrous oxide Remember: the vowel “A” on the prefix tetra- is dropped because oxide starts with the vowel “O.”

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