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Unformatted text preview: Lec-8: Limiting reactants & Combustion analysis Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 1 Combustion Analysis he percent of carbon and hydrogen in ydrocarbons ( The percent of carbon and hydrogen in hydrocarbons (C a H b ) can be determined from the mass of H 2 O and CO 2 produced. C H + excess O---> a CO (g) + b/2 H O a b 2 2 (g) 2 eg. C 6 H 14 + excess O 2 6CO 2 (g) + 7H 2 O Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 2 Combustion analysis of an unknown compound indicated that it is 92.23% C and 7.82% H. The mass spectrum dicated the molar mass is 78 g/mol What is the indicated the molar mass is 78 g/mol. What is the molecular formula of this unknown compound? Assume 100g of unknown 92.23g C and 7.82g H 1mol oles C = 92.23g 7.679mol = moles C 92.23g 7.679mol 12.01 1mol moles H = 7.82g 7.82mol .0 g = Empirical formula = CH 1.0 g Molecular formula is a simple multiple n of the empirical formula 78 / mol n 6 13 / mol g g = = Molecular formula is...
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