CHEM 1021 Lecture Notes - Lecture 19: Chromate And Dichromate, Ionic Compound, Molar Mass
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Review chapter 2 sections 2. 2-2. 5, all of chapter 3 and 4. Exam on tuesday 10/11/16 from 7 to 8:30 pm. Determining molecular formulas from elemental analysis and molar mass. Analysis of a hydrocarbon shows 95. 21 mass percent carbon. Find the empirical and molecular formula of the hydrocarbon if its molar mass is 252. 30 g/mol. Carbon: (95. 21 g c) (1 mol c/12. 01 g) = 7. 927 mol c. Hydrogen: 100- 95. 21 = 4. 79 g h (4. 79 g h) (1 mol h/1. 008 g) = 4. 75 mol h. Divide by the smallest (7. 927 mol c/4. 75 mol h) = 1. 668 mol c/ 1 mol h. C1. 668 h, ---> c1. 668 x 3 h3 ----> c5h3. Mm for c5h3 = 5(12. 01) + 3(1. 008) = 63. 07 g/mol (252. 30 g/mol)/(63. 07 g/mol) = 4. A 856g sample of a compound containing iron, chromium, and oxygen was found to contain: Which conversion factors would you need to find the percent mass of oxygen in this compound? (review problem)
