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PPT Ch3 Z&amp;Z

# PPT Ch3 Z&amp;Z - STOICHIOMETRY The Mole Atomic and...

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STOICHIOMETRY The Mole Atomic and Molecular Masses Chemical Formula Stoichiometry

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ATOMIC MASS Atomic mass standard is based on the atom Carbon-12 or 12 C (6 p + , 6 n 0 , 6 e - ). One C-12 atom weighs exactly 12 amu 1 amu = atomic mass unit = 1.661E-27 kg
ATOMIC WEIGHT Atomic weight (mass) of an element is defined as a weighted average over all naturally occurring isotopes of the element; this is the number on bottom on each element box on the Periodic Table.

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Calculate the Atomic Weight of Boron Boron has two naturally occurring isotopes. 10 B has a mass of M 1 = 10.0129 amu and abundance of A 1 = 19.78%. 11 B has a mass of M 2 = 11.0093 amu and abundance of A 2 = 80.22%. • At. Wt = Σ (M i x A i )/100 = [10.0129 x 19.78 + 11.0093 x 80.22]/100 = 10.81 amu (see PT)
MOLE The number of C-12 atoms in exactly 12 grams of pure C-12 6.022E+23 items Avogadro’s Number, N A mole of an element has a mass equal to its average atomic weight (mass). 1 mol of naturally occurring Boron has a mass of 10.81 g.

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MOLECULE and MOLAR MASS Molecule = arrangement of atoms chemically bonded together. Molar Mass = Sum of atomic masses of constituent atoms in one molecule (amu) or one mole of molecules (gram). Use atomic and molar masses to the 1/100 place.
CHEMICAL FORMULA Qualitative description of the constituent elements in a molecule or ion. – C

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PPT Ch3 Z&amp;Z - STOICHIOMETRY The Mole Atomic and...

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