Chapter 3 Notes

# Chapter 3 Notes - C HAPTER 3 S TOICHIOMETRY 19 A UGUST 2009...

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Unformatted text preview: C HAPTER 3: S TOICHIOMETRY 19 A UGUST 2009 Dr. Charlie Cox CHEM 1310 - G Fall 2009 1 Mix Reagents Chemical reaction C HAPTER 3 S TOICHIOMETRY C HAPTER O BJECTIVES 3.1: Describe how atomic masses are computed using mass spectrometry and the role of isotopes in this computation. 3.2: Define the mole and explain why it is important in chemistry. 3.3: Develop the idea of molar mass and provide sample calculations. 3.4: Discuss the concept of percent composition with supporting examples. 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: Introduce the concept of chemical equations and methods used to balance the equations with a discussion of the importance of balancing equations. 3.7: Provide examples of stoichiometry calculations which will be emphasized throughout the semester. 3.8: Emphasize the significance of limiting reagents and discuss theoretical and percent yields. 2 3.1: A TOMIC M ASSES 19 th Century Chemists calculated relative atomic masses 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 spectrometer – accurate method to compare masses of atoms 3 Mass of 13 C = 13.003 amu M + e – (70 eV) M + + 2e – M + lower mass ions M ASS S PECTROMETRY AND I SOTOPES Mass Spectrometer accelerates ions (or molecular ions) in an electric field and then separates those ions by relative mass in a magnetic field 4 Mass Spectrometer Separation of Chlorine 20 40 60 80 100 35 37 Relative Mass Relative Amount 17 35.45 Cl Chlorine 3 1 Weighted Atomic Mass: 5 Isotopes of Cl: 031 150 msec EC/ECp,11.98 S-31 / P-30 30.9924 032 298 msec EC/ECa/ECp,12.6 85 S-32 / Si-28 / P-31 31.985688 033 2.511 sec EC,5.583 MeV S-33 32.97745 034 1.5264 sec EC,5.492 MeV S-34 33.97376 035 75.77% Stable 34.9688 036 3.01E+5 yr B- /EC,10.413 Ar-36 / S-36 35.9683 037 24.23% Stable 36.9659 038 37.24 min B-,4.917 MeV Ar-38 37.968010 039 55.6 min B-,3.442 MeV Ar-39 38.968008 040 1.35 min B-,7.480 MeV Ar-40 39.970413 041 38.4 sec B-,5.730 MeV Ar-41 40.970649 042 6.8 sec B-,9.430 MeV Ar-42 41.973172 043 3.3 sec B-,7.950 MeV Ar-43 42.974202 044 0.43 sec B-/B- n,3.920 Ar-44 / Ar-43 43.978539 045 400 msec B-/B-n,10.800 Ar-45 / Ar-44 44.979710 046 0.22 sec B-/B-n,6.900 Ar-46 / Ar-45 45.984111 47 200 nsec B-/B- n,14.700 Ar-47...
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## This note was uploaded on 04/12/2010 for the course CS 1371 taught by Professor Stallworth during the Spring '08 term at Georgia Tech.

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Chapter 3 Notes - C HAPTER 3 S TOICHIOMETRY 19 A UGUST 2009...

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