# molecular mass by K2Tytb9

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schedule
330 03’03: Molecular Mass

CORRELATIONS
National Content Standards:
Connecticut Standards:
Ridgefield Themes:

ESSENTIAL CONCEPT
Atomic Mass and Molar Mass
“The mass of an atom, which is extremely small, is based on the carbon-12 isotope scale. An atom of the
carbon-12 isotope was assigned a mass of exactly 12 atomic mass units (amu). To work with the more
convenient scale of grams, chemists use the molar mass. The molar mass of carbon-12 is exactly 12 g
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and contains an Avogradro’s number (6.022 x 10 ) of atoms. The molar masses of other elements are
also expressed in grams and contain the same number of atoms. The molar mass of a molecule is the sum
of the molar masses of its constituent atoms.”1

HOMEWORK:
DUE:
DO:

REVIEW:
1. Atomic mass unit = mass of an atom in amu
2. 1 amu  1/12th the mass of one C-12 atom
n
3. average atomic mass =          (abundance * mass )
i 1
eachisotope

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4. 1 mol (Avogadro’s Number, NA) = 6.02 x 10
5. mass  mole  number of particles
6. molecular mass (formula mass)

LESSON:
§03.04: Mass Spectrometer
1. mass spectrometer:
A. instrument used to measure the masses and relative concentrations of atoms, molecular fragments
and molecules.
B. e.g.,                         urea would split into C=O, C-NH2, NH2, etc.

C. e.g., how to determine natural abundances of isotopes of a given element.

1
Yang, R. (2008). Chapter 2: Atoms, Molecules, and Ions. In General Chemistry: The Essential Concepts (5th ed.,
p. 28). New York: McGraw Hill.
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