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Unformatted text preview: Chem 1P Lecture 13: Mass percent Measuring compounds Measuring compounds What is it? Mass spectrometer Chang Section 3.43.5 Mass percent Mass percent of C = mass of C in 1 mol compound mass of 1 mol compound x 100% What is the percentage of each element in a compound by mass? This is another way of expressing the relative amounts of different elements in a compound. Chang Section 3.43.5 Mass percent 1 mol = 180.156 g Mass of C: Mass of H: Mass of O: 6 mol x 12.01 g/mol 12 mol x 1.008 g/mol 6 mol x 16.00 g/mol = 72.06 g C = 12.096 g H = 96.00 g O First determine molar mass: 180.16 g C 6 H 12 O 6 What are the mass percentages of the elements in glucose? Chang Section 3.43.5 Mass percent C 6 H 12 O 6 Mass percent of C = Mass percent of H = Mass percent of O = 72.06 g C 180.16 g C 6 H 12 O 6 x 100% = 40.00% 12.096 g H 180.16 g C 6 H 12 O 6 x 100% = 6.714% 96.00 g O 180.16 g C 6 H 12 O 6 x 100% = 53.29% 100.004% 100.00% Chang Section 3.43.5 Mass percent C 11 H 13 ClN 2 Epibpedobates tricolor 1 mol = 208.68 g Mass of C: Mass of H: Mass of Cl: Mass of N: 11 mol x 12.01 g/mol 13 mol x 1.008 g/mol 1 mol x 35.45 g/mol 2 mol x 14.01 g/mol Epibatidine is a poisonous compound found in the skins of some South American frogs. = 132.11 g C = 13.104 g H = 35.45 g Cl = 28.02 g N What are the mass percentages in epibatidine? Chang Section 3.43.5 Mass percent C 11 H 13 ClN 2 Mass percent of C = Mass percent of H = Mass percent of Cl = Mass percent of N = 132.11 g C 208.68 g C 11 H 13 ClN 2 x 100% = 63.31% 13.104 g H 208.68 g C 11 H 13 ClN 2 x 100% = 6.279% 35.45 g Cl 208.68 g C 11 H 13 ClN 2 x 100% = 16.99% 28.02 g N 208.68 g C 11 H 13 ClN 2 x 100% = 13.43% 100.009% ~100.0% Chang Section 3.43.5 Empirical formula...
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This note was uploaded on 11/23/2010 for the course CHEM Chem 1P taught by Professor Ericpotma during the Winter '10 term at UC Irvine.
 Winter '10
 EricPotma
 Chemistry

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