Unformatted text preview: MOLECULAR WEIGHT AND MOLAR MASS
Molecular weight is the sum of the is
atomic weights of all atoms in the molecule. What is the molar mass of ethanol, C 2H6O? 1 mol contains
2 mol C (12.01 g C/1 mol) = 24.02 g C mol) 6 mol H (1.01 g H/1 mol) = 6.06 g H mol) 1 mol O (16.00 g O/1 mol) = 16.00 g O mol) TOTAL = molar mass = 46.08 g/ mol Tylenol Tylenol Molar mass = molecular weight in molecular
grams • Formula = C8H9NO2 • Molar mass = 151.2 g/mol How many moles of alcohol are there in a “standard” can of beer if there are 21.3 g of C 2H6O?
(a) Molar mass of C 2H6O = 46.08 g/mol (b) Calc. moles of alcohol
21.3 g • 1 mol = 0 .462 mol 46.08 g How many molecules of alcohol molecules of are there in a “standard” can of beer if there are 21.3 g of C 2H6O?
We know there are 0.462 mol of C 2H6O.
0.462 mol • 6.022 x 10 23 molecules 1 mol How many atoms of C are there in How atoms are a “standard” can of beer if there are 21.3 g of C 2H6O?
We know there are 2.78 x 10 23 molecules. Each molecule contains 2 C atoms. Therefore, the number of C atoms is
2.78 x 10 23 m olecules • 2 C atoms 1 molecule = 2.78 x 10 23 molecules = 5.57 x 10 23 C atoms Page 1 ...
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 Fall '08
 POZIKRIZDIS
 Atom, Mole, Molecule, Atomic mass unit

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