The Mole, Percent Composition, and Formulas

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What is a mole in chemistry?

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A mole is a unit of measurement used to express the amount of a substance. It is defined as the amount of substance that contains as many entities (atoms, molecules, etc.) as there are in 12 grams of carbon-12.

Front

What is the formula to 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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How do you determine the empirical formula from percent composition?

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1. Convert percent to grams. 2. Convert grams to moles. 3. Divide by the smallest number of moles to find the simplest ratio.

Front

What is the molar mass of NaCl?

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58.45 g/mol.

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How many molecules are in 1 mole of a substance?

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1 mole of a substance contains 6.022 x 10^23 molecules (Avogadro's number).

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What is the relationship between moles and mass?

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Mass (g) = Moles x Molar Mass (g/mol).

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How do you convert moles to grams?

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To convert moles to grams, multiply the number of moles by the molar mass of the substance.

Front

What is the empirical formula of a compound with 72.2% magnesium and 27.8% nitrogen?

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Mg3N2.

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How do you find the number of atoms in a given mass of an element?

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1. Convert mass to moles using molar mass. 2. Multiply moles by Avogadro's number.

Front

What is the empirical formula for a compound with 42.07% Na, 18.89% P, and 39.04% O?

Back

Na3PO4.