Empirical/Molecular Formulas and Percent Composition

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What is an empirical formula?

Back

An empirical formula represents the simplest whole-number ratio of atoms of each element in a compound.

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What is a molecular formula?

Back

A molecular formula shows the actual number of atoms of each element in a molecule of a compound.

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How do you determine the molecular formula from the empirical formula?

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To find the molecular formula, multiply the subscripts in the empirical formula by a whole number (n) that is the ratio of the molar mass of the compound to the molar mass of the empirical formula.

Front

What is the molar mass of CH4?

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The molar mass of CH4 (methane) is 16.05 g/mol.

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What is the molar mass of AlCl3 * 6 H2O?

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The molar mass is calculated as 26.98 + (3 x 35.45) + (6 x 18.02) = 241.43 g/mol.

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What is percent composition?

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Percent composition is the percentage by mass of each element in a compound.

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How do you calculate percent composition?

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Percent composition = (mass of element in 1 mole of compound / molar mass of compound) x 100.

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What is a hydrate?

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A hydrate is an ionic compound that contains water molecules within its crystal structure.

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How do you find the percent water in a hydrate?

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Percent water = [(mass of water in the formula) / (molar mass of the hydrate)] x 100.

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What is the significance of molar mass in chemistry?

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Molar mass is used to convert between grams and moles of a substance, which is essential for stoichiometric calculations.