Scan_Doc0096 - it into its component elements or reacting...

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90 Chapter Three Stoichiometry How do we get there? What is the mass of each element in 1 mol C 1o H 14 0? 120.1 g + 14.11 g + 16.00 g = 150.2 g C lO + HI4 + 0 = C lO H I4 0 What is the mass percent of each element? We find the fraction of the total mass contributed by each element and convert it to a percentage: Mass of C in 1 mol = 10 mot X 12.01!r Mass ofH in 1 mol = 14 mot X 1.008!r = 14.11 g Mass of 0 in 1 mol = 1 mot X l6.00!r = 16.00 g 120.1 g What is the molar mass of C lO H 14 0? Carvone 120.1 g C Mass percent of C = X 100% = 79.96% 150.2 g C lO H 14 0 14.11 g H Mass percent of H = X 100% = 9.394% 150.2 g C 1o H I4 0 16.00 g 0 Mass percent of 0 = X 100% = 10.65 % 150.2 g C lO H I4 0 Reality Check: Sum the individual mass percent values-they should total to 100% within round-off errors. In this case, the percentages add up to 100.00%. SEE EXERCISES 3.67 AND 3.68 3.7 ~ Determining the Formula of a Compound When a new compound is prepared, one of the first items of interest is the formula of the compound. This is most often determined by taking a weighed sample of the compound and either decomposing
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Unformatted text preview: it into its component elements or reacting it with oxygen to produce substances such as CO 2 , H 2 0, and N 2 , which are then collected and weighed. A device for doing this type of analysis is shown in Fig. 3.5. The results of such analyses provide the mass of each type of element in the compound, which can be used to determine the mass percent of each element. Furnace CO 2 , H 2 0, 02, and other gases O 2 and other gases 1-O 2 Figure 3.5 A schematic diagram of the combustion device used to analyze substances for carbon and hydrogen. The sample is burned in the presence of excess oxygen, which converts all its carbon to carbon dioxide and all its hydrogen to water. These products are collected by absorption using appropriate materials, and their amounts are determined by measuring the increase in masses of the absorbents....
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