17Sept2008QuizSol

# 17Sept2008QuizSol - Chapter 2 Atoms Molecules and Ions 2.1...

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1 Chapter 2 Atoms, Molecules and Ions Atoms, Molecules and Ions 2.1 The Early History of Chemistry 2.2 Fundamental Chemical Laws 2.3 Dalton’s Atomic Theory 2.4 Cannizzaro’s Interpretation 2.5 Early Experiments to Characterize the Atom 2.6 The Modern View of Atomic Structure: An Introduction 2.7 Molecules and Ions 2.8 An Introduction to the Periodic Table 2.9 Naming Simple Compounds Chapter 3 ( Chapter 3 ( Stoichiometry Stoichiometry ): Objectives ): Objectives 3.1: 3.1: Describe how atomic masses are computed using mass spectrometry and the role of isotopes in this computation. 3.2: 3.2: Define the mole and explain why it is important in chemistry. 3.3: 3.3: Develop the idea of molar mass and provide sample calculations. 3.4: 3.4: Discuss the concept of percent composition with supporting examples. 3.5: 3.5: Explain how the concepts of the mole and molar mass are used collectively to identify the chemical formula of an unknown. 3.6: 3.6: Introduce the concept of chemical equations and methods used to balance the equations with a discussion of the importance of balancing equations. 3.7: 3.7: Provide examples of stoichiometry calculations which will be emphasized throughout the semester. 3.8: 3.8: Emphasize the significance of limiting reagents and discuss theoretical and percent yields.

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2 Zumdahl Chapter 3 3 Atomic Masses Atomic Masses 19 th Century Chemists evaluated relative atomic masses (see Chptr. 2) 1961 modern system of atomic masses: 12 C is assigned a mass of exactly 12 atomic mass units (amu) and the masses of all other atoms are relative to this standard Mass spectrometry : An accurate method to measure & compare masses of atoms m( 13 C) = 1.083613 m( 12 C) = 13.00336 amu = 2.159258 x 10 23 grams M + e (70 eV) M + + 2e M + lower mass ions Mass of one 12 12 C atom = 1.992647 x 10 23 23 grams 8/19/2009 Zumdahl Chapter 3 Mass Spectrometry and Isotopes Mass Spectrometry and Isotopes • The mass spectrometer accelerates ions in an electric field and then separates those ions by relative mass (actually mass/charge) in a magnetic field. Mass Spectrometer Separation of Chlorine 0 20 40 60 80 100 35 37 Relative Mass Relative Amount 17 35.45 Cl Chlorine 1 1 + 2 2 + . .. + n n Average Rela tive A tom ic Mass = AP AP AP Chlorine = 35 x 75.77% + 37 x 24.23% Chlorine =26.52+8.97 Chlorine =35.49 3 1
3 8/19/2009 Zumdahl Chapter 3 Known Isotopes of Cl: Known Isotopes of Cl: MASS abund. Halflife Particle, Energy Decay Product(s) Isotopic Mass 0 47 200 nsec B-/B- n,14.700 Ar-47 / Ar-46 46.987976 046 0.22 sec B-/B-n,6.900 Ar-46 / Ar-45 45.984111 045 400 msec B-/B-n,10.800 Ar-45 / Ar-44 44.979710 044 0.43 sec B-/B- n,3.920 Ar-44 / Ar-43 43.978539 043 3.3 sec B-,7.950 MeV Ar-43 42.974202 042 6.8 sec B-,9.430 MeV Ar-42 41.973172 041 38.4 sec B-,5.730 MeV Ar-41 40.970649 040 1.35 min B-,7.480 MeV Ar-40 39.970413 039 55.6 min B-,3.442 MeV Ar-39 38.968008 038 37.24 min B-,4.917 MeV Ar-38 37.968010 037 24.23% Stable 36.9659 036 3.01E+5 yr B- /EC,10.413 Ar-36 / S-36 35.9683 035 75.77% Stable 34.9688 034 1.5264 sec EC,5.492 MeV S-34 33.97376 033 2.511 sec EC,5.583 MeV S-33 32.97745 032 298 msec EC/ECa/ECp,12.6 85 S-32 / Si-28 / P-31 31.985688 031 150 msec EC/ECp,11.9 80 S-31 / P-30 30.9924 35 Cl contains 17 protons and 18 neutrons 37 Cl contains 17 protons and 20 neutrons 1 1 + 2 2 + . .. + n n Average Rela tive A tom ic Mass = AP AP AP Chlorine = 35.45 Avogadro Avogadro ’s Number and the Mole s Number and the Mole The mass, in grams, of 1 mole of atoms of an element is numerically equal to the relative atomic mass

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17Sept2008QuizSol - Chapter 2 Atoms Molecules and Ions 2.1...

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