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Using the Ideal Gas Law and Previously Learned Concepts . A gas that is 80.0% carbon and 20.0% hydrogen has a density of 1.339 g/L at STP. Use this info. to calculate its Molecular Weight in g/mol Empirical Formula Molecular Formula Answers: MW = 30.0 g/mol E.F. = CH 3 M.F. = C 2 H 6.
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Using the Ideal Gas Law and Previously Learned Concepts • A gas that is 80.0% carbon and 20.0% hydrogen has a density of 1.339 g/L at STP. Use this info. to calculate its • Molecular Weight in g/mol • Empirical Formula • Molecular Formula • Answers: • MW = 30.0 g/mol • E.F. = CH3 • M.F. = C2H6
Figure 5.11 Determining the molar mass of an unknown volatile liquid based on the method of J.B.A. Dumas (1800-1884)
Dumas Method of Molar Mass Problem: A volatile liquid is placed in a flask whose volume is 590.0 ml and allowed to boil until all of the liquid is gone, and only vapor fills the flask at a temperature of 100.0 oC and 736 mm Hg pressure. If the mass of the flask before and after the experiment was 148.375g and 149.457 g, what is the molar mass of the liquid? Answer: Molar Mass = = 58.03 g/mol