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Ch3_MolarMass

# Ch3_MolarMass - MOLECULAR WEIGHT AND MOLAR MASS Molecular...

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