# percent composition and chemical formulas - composition and chemical formulas ... percent...

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chemistry

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Percent Composition and Chemical Formulas

It helps to know the percents of the components in a shirt because they affect how warm it is, whether it will need to be ironed, and how it should be cleaned. You will learn how the percents of the elements in a compound are important in chemistry.

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Percent Composition and Chemical Formulas

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The Percent Composition of a Compound

The Percent Composition of a Compound

How do you calculate the percent by mass of an element in a compound?

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Percent Composition and Chemical Formulas

> The Percent Composition of a Compound

The percent by mass of an element in a compound is the number of grams of the element divided by the mass in grams of the compound, multiplied by 100%.

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Percent Composition and Chemical Formulas

> The Percent Composition of a Compound

Percent Composition from Mass Data

The relative amounts of the elements in a compound are expressed as the percent composition or the percent by mass of each element in the compound.

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SAMPLE PROBLEM

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Percent Composition and Chemical Formulas

> The Percent Composition of a Compound

Percent Composition from the Chemical Formula

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SAMPLE PROBLEM

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Percent Composition and Chemical Formulas

> The Percent Composition of a Compound

Percent Composition as a Conversion Factor

You can use percent composition to calculate the number of grams of any element in a specific mass of a compound.

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Percent Composition and Chemical Formulas

> The Percent Composition of a Compound

Propane (C3H8) is 81.8% carbon and 18% hydrogen. You can calculate the mass of carbon and the mass of hydrogen in an 82.0 g sample of C3H8.

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Percent Composition and Chemical Formulas

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Empirical Formulas

Empirical Formulas

What does the empirical formula of a compound show?

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Percent Composition and Chemical Formulas

> Empirical Formulas

The empirical formula gives the lowest whole-number ratio of the atoms of the elements in a compound.

The empirical formula of a compound shows the smallest whole-number ratio of the atoms in the compound.

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Percent Composition and Chemical Formulas

> Empirical Formulas

Ethyne (C2H2) is a gas used in welders torches. Styrene (C8H8) is used in making polystyrene.

These two compounds of carbon have the same empirical formula (CH) but different molecular formulas.

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Percent Composition and Chemical Formulas

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Molecular Formulas

Molecular Formulas

How does the molecular formula of a compound compare with the empirical formula?

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Percent Composition and Chemical Formulas

> Molecular Formulas

The molecular formula of a compound is either the same as its experimentally determined empirical formula, or it is a simple whole-number multiple of its empirical formula.

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Percent Composition and Chemical Formulas

> Molecular Formulas 10.3

Methanal, ethanoic acid, and glucose all have the same empirical formulaCH2O.

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Percent Composition and Chemical Formulas

> Molecular Formulas 10.3

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