204mole - The Mole Concept Glenn V. Lo Department of...

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    The Mole Concept Glenn V. Lo Department of Physical Sciences Nicholls State University
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Atomic Masses Mass Spectrometer – instrument used to measure  masses of atoms and molecules Reference:  12 C isotope is exactly 12 amu (or u) Mass Number is NOT equal to atomic mass in amu Mass of  13 C: 13.003354826 amu Mass of  35 Cl: 34.969 amu Data:  http://www.webelements.com To nearest whole number, mass of an atom in amu is  equal to mass number “Atomic mass” shown in periodic table: average mass  of atoms in a naturally-occurring sample
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Atomic Masses Naturally-occurring sample of carbon is:  98.93%  12 C, 1.07%  13 C What atomic mass is shown in the periodic table for C : C-12 is 12 u exactly C-13 is 13.003354826 u  Avg=(12)(0.9893)+(13.003354826)(0.0107)  Atomic mass = 12.011 u
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Atomic Masses Naturally occurring hydrogen is primarily  1 H (protium; 1.0078 u)  and  2 H (deuterium; 2.0141 u).  Since the tabulated atomic mass  of H is 1.008, calculate the relative abundance of protium and  deuterium.  Data can be found at  http://www.webelements.com Avg Mass = ( 1 H mass)(%protium)  + ( 2 H mass)(%deuterium) 1.008 = (1.0078)(x)+(2.0141)(1-x)  x = ?
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The Mole Concept Mole = how we count atoms,  molecules, and ions Definition:  One mole of  12 atoms has a mass of exactly  12 g. How many atoms are in one  mole of  12 C? We do not know exactly, but 
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This note was uploaded on 06/11/2009 for the course CHEM 105 taught by Professor Wessel during the Spring '08 term at Nicholls State.

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204mole - The Mole Concept Glenn V. Lo Department of...

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