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10 Cards in this Set
- Front
- Back
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Avagadro's number =
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6.022 x 10²³
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Mass % composition of compounds:
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mass of X in a sample of the compound / mass of the sample of the compound x 100
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Mass % composition from a chemical formula:
Mass % of element X = |
Mass of element X in 1 mol of a compound / mass of 1 mol of compound x 100
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You can calculate the mass percent composition from a molecular formula; can you calculate a chemical formula from mass percent composition?
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yes, but it will be an Empirical Formula
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If you calculate a chemical formula from a mass% composition, you will get:
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an empirical formula
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What is the empirical formula?
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It is a chemical formula derived from the mass% composition.
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How do you obtain an empirical formula from g.?
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1) convert g of substances to moles.
2) write the pseudoformula of the compound. 3) divide all the subscripts by the smallest subscript. 4) if not whole numbers after dividing, multiply to get whole number. |
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You can obtain the molecular formula of a compound from the empirical formula, if you also know:
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the molecular formula molar mass of the compound
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n =
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Molecular formula Molar mass / empirical formula molar mass
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Molecular formula =
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Empirical formula x n
where n = a positive integer. |
