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Unformatted text preview: Mass Percent The Mass Percent of a component is defined What is the mass percents of carbon, hydrogen, and oxygen in pure ethanol C 2 H 6 O? First we calculate the mass of one mole of C 2 H 6 O... mass of 2 moles of C is 2 X 12.011 g mass of 6 moles of H is 6 X 1.008 g mass of 1 mole of O is 15.999 g Molecular weight of C 2 H 6 O is 46.069 g Next we calculate the mass percents Note that the mass percentages should add up to 100%. Combustion Analysis When chemists make new compounds one of the first things they often do is determine the mass % for the different elements in the compound. To analyze the mass percent of carbon and hydrogen chemist use a combustion device. The sample is burned in the presence of excess oxygen which converts all the carbon to carbon dioxide and all the hydrogen to water. The CO 2 and H 2 O produced are absorbed in two different stages and their masses determined by measuring the increase in weight of the...
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