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userdata-paziras-Chem101-Chap_03A

# 09gcu 7955gcuo 4 seawatercontains00065by massofbromine

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Unformatted text preview: 6 % Cl = 100.00 % How many mg of Na are contained in 2,000. mg NaCl ? 39.34 mg Na ? mg Na = 2,000. mg NaCl x ¾¾¾¾¾¾ = 786.8 mg Na 100.00 mg NaCl 6 Chemistry 101 Chapter 3 Examples: 1. Calculate the percent composit ion of sodium phosphate (Na3PO4). Calculate mo lar mass of sodium phosphate: 3 mo les Na 1 mo le P 4 mo les O 1 mo le Na3PO4 = = = = % Na = ¾¾¾¾¾¾¾¾¾¾¾ x 100 = % P = ¾¾¾¾¾¾¾¾¾¾¾ x 100 = % O = ¾¾¾¾¾¾¾¾¾¾¾ x 100 = TOTAL % = 100.00 % 2. Calculate the mass percentage of copper in the natural ore malachite. The formula of malachite is CuCO3 . Cu(OH)2 First: Calculate the mass of 1 mo le of CuCO3 . Cu(OH)2 2 mo les Cu = 2 x 63.55 g = 127.1 g Cu 1 mo le C = 1 x12.01 g = 12.01 g C 5 mo les O = 5 x 16.00 g = 80.00 g O 2 mo les H = 2 x 1.01 g = 2.02 g H 1 mo le CuCO3 . Cu(OH)2 % Cu = = 221.1 g 127.1 g x 100 = 57.49% 221.1 g 7 Chemistry 101 Chapter 3 3. Calculate the mass of copper in 1.37 grams of copper (II) oxide (CuO) 1 mo le Cu 1 mo le O = = 1 x 63.55 g 1 x 16.00 g 1 mo le CuO = = 63.55 g 16.00 g = 79.55 g 63.55 g Cu ? g Cu = 1.37 g CuO x ¾¾¾¾¾¾ = 1.09 g Cu 79.55 g CuO 4. Seawater contains 0.0065% (by mass) of bromine. How many grams of bromine are there in 2.50 L of 3 seawater? The densit y o f seawater is 1.025 g/cm . 8 Chemistry 101 Chapter 3 CHEMICAL FORMULAS · Formulas give information about the type, the number, and arrangement o...
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