EXAMPLE 3.6 Juglone 3.4 Molar Mass 85 molecules, we need a special name for the fundamental unit of these materials. Instead of molecule, we use the term formula unit. Thus CaC0 3 is the formula unit for calcium carbonate, and NaCl is the formula unit for sodium chloride. Juglone, a dye known for centuries, is produced from the husks of black walnuts. It is also a natural herbicide (weed killer) that kills off competitive plants around the black walnut tree but does not affect grass and other noncompetitive plants. The formula for juglone is CjQH 60 3 • a. Calculate the molar mass of juglone. b. A sample of 1.56 X 10-2 g of pure juglone was extracted from black walnut husks. How many moles of juglone does this sample represent? Solution a. The molar mass is obtained by summing the masses of the component atoms. In 1 mole of juglone there are 10 moles of carbon atoms, 6 moles of hydrogen atoms, and 3 moles of oxygen atoms: 10 C: 10 X 12.01 g = 120.1 g 6 H: 6 X 1.008 g = 6.048 g 3 0: 3
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This note was uploaded on 12/13/2010 for the course CHEM 2301 taught by Professor Bill during the Spring '10 term at South Texas College.