Mole/Percent Composition/Empirical and Molecular Formula

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What is a mole in chemistry?

Back

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.

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What is Avogadro's number?

Back

Avogadro's number is 6.02 x 10^23, which is the number of particles (atoms, molecules, etc.) in one mole of a substance.

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How do you calculate the molar mass of a compound?

Back

To calculate the molar mass, sum the atomic masses of all the atoms in the compound's formula, using the periodic table.

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What is the empirical formula?

Back

The empirical formula is the simplest whole-number ratio of the elements in a compound.

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What is the molecular formula?

Back

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

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How do you find the percent composition of an element in a compound?

Back

Percent composition is calculated by dividing the mass of the element in one mole of the compound by the molar mass of the compound, then multiplying by 100.

Front

Calculate the molar mass of NaCl.

Back

The molar mass of NaCl is approximately 58.44 g/mol (22.99 g/mol for Na + 35.45 g/mol for Cl).

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What is the percent composition of chlorine in NaCl?

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The percent composition of chlorine in NaCl is approximately 60.66%.

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How many moles are in 12 grams of carbon?

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There are 1 mole of carbon in 12 grams, since the molar mass of carbon is 12 g/mol.

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How many molecules are in 1 mole of water (H2O)?

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There are 6.02 x 10^23 molecules in 1 mole of water.