A solid carbohydrate (C a H b O c ) with a specific gravity of 1.59 is

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A solid carbohydrate (CaHbOc) with a specific gravity of 1.59 is placed in a 1.000-liter combustion chamber. The chamber is evacuated and then charged with pure oxygen. Complete combustion of the carbohydrate takes place. A sample of the product gas is cooled to condense all the water formed in the combustion, and the remaining gas is analyzed by gas chromatography. The following data are obtained:

Mass of Carbohydrate Charged:                                  3.42 g

Chamber Conditions Prior to Combustion:                T = 26.8°C, P 499.9 kPa

Chamber Conditions Following Combustion:            T = 483.4°C, P = 1950.0 kPa

Product Gas Analysis:                                                     38.7 mole % CO2. 25.8% O2, 355% H2O

Assume (i) none of the carbohydrate is lost when the chamber is evacuated and (ii) the vapor pressure of the carbohydrate at 27°C is negligible. Do not neglect the volume of the carbohydrate and do not assume ideal gas behavior.

(a) Determine at least two possible molecular formulas for the carbohydrate (i.e.. sets of integer values of a, b, arid c) consistent with the given data.

(b) If the molecular weight of the carbohydrate is independently determined to be in the range 300 to 350, what is its molecular formula?

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Elementary Principles of Chemical Processes

ISBN: 978-0471720638

3rd Edition

Authors: Richard M. Felder, Ronald W. Rousseau

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