Week 2 Practice Problems

Week 2 Practice Problems - CHEMISTRY 201X Practice Problems...

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CHEMISTRY 201X August 27-31, 2007 Practice Problems (15) Locate the following elements in the Periodic Table; indicate whether it is a metal, metalloid, or nonmetal; identify common charges its ions may adopt. (a) Chromium (b) Xenon (c) Phosphorus (d) Zinc (e) Arsenic (f) Gallium (16) Calculate the percentage by mass of the indicated element in the corresponding compound: (a) carbon in ascorbic acid, HC 6 H 7 O 6 ; (b) nitrogen in ammonium sulfate; (c) tin in tin(II) fluoride; (d) sodium in sodium chloride. (17) Determine the empirical and molecular formulas of each of the following substances: (a) Epinephrine, which contains 59.0% C, 7.1% H, 26.2% O and 7.7% N by mass. Its MW is approximately 180 g/mol. (b) Caffeine, which contains 49.5% C, 5.15% H, 28.9% N and 16.5% O by mass. Its MW is approximately 195 g/mol. (18) A sample of an oxide of iron weighing 1.60 g was heated in a stream of hydrogen gas until it was completely converted into 1.12 g of metallic iron. (a) What do you think happened to the oxygen in the oxide?
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Week 2 Practice Problems - CHEMISTRY 201X Practice Problems...

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