Lecture 17, Percent Composition


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Percent Composition

  1. Calculate the percent mass of each element for the given chemical formula:
    1. NaCl
    2. H2O
    3. CFCl3

  2. Determination of Formula:
    1. What is the emperical formula of a salt. 100.0000 grams of salt is analyzed and found to contain:
      1. >39.3374 grams of sodium
      2. 60.6626 grams of chloride

    2. What is the emperical formula of an alcohol. 69.8457 grams of AN alcohol is analyzed and found to contain:
      1. 41.9124 grams carbon
      2. 9.3234 grams hydrogen
      3. 18.6100 grams oxygen

    3. What is the molecular formula of the alcohol if:
      1. MW = 60.05 grams/mole
      2. MW = 120.10 grams/mole

    4. 1 asprin tablet contains 325 mg of acetylsalicylic acid (C9H8O4, see page 220 in textbook for structure).
      1. How many moles of asprin, carbon, hydrogen, and oxygen are in a single tablet?
      2. How many atoms(molecules) of asprin, carbon, hydrogen and oxygen are in a single tablet?
      3. What is the percent composition of acetylsalicylic acid?


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Department of Chemistry
Widener University
Chester, PA 19013

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