Learning ObjectiveTranslate between a molecular formula that a compound and also its percent composition by mass
Key PointsThe atom composition of chemistry compounds deserve to be described in a variety of ways, consisting of molecular formulas and also percent composition.The percent ingredient of a compound is calculated through the molecular formula: divide the massive of each element found in one mole the the link by the complete molar fixed of the compound.The percent composition of a compound have the right to be measure experimentally, and also these values can be offered to recognize the empirical formula that a compound.

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Termpercent by massthe fraction, through weight, the one element of a compound.

The atom composition of chemical compounds have the right to be defined using a variety of notations including molecular, empirical, and structural formulas. One more convenient way to describe atomic ingredient is to research the percent composition of a compound by mass.

## Percent ingredient by Mass

Percent composition is calculated native a molecule formula by dividing the massive of a solitary element in one mole that a link by the fixed of one mole that the entire compound. This worth is presented together a percentage.

Percentage ingredient – YouTubeThis video clip shows just how to calculate the percent ingredient of a compound.

For example, butane has a molecule formula that C4H10. Butane’s percent composition deserve to be calculated as follows:

Mass the H every mol butane: 10:mol:H cdot frac1.00794:g1:mol: H = 10.079:g:HMass of C every mol butane: 4:mol:Ccdotfrac12.011:g:C1:mol:C=48.044:g:CMass percent H in butane: frac10.079:g:H58.123:g:butane cdot 100 = 17.3% HMass percent C in butane: frac 48.044:g :C 58.123 :g :butane cdot 100 = 82.7% C

Therefore, the atom composition that butane can also be defined as 17.3% hydrogen and also 82.7% carbon, and, as expected, these values amount to 100%.

ButaneThe structure formula of butane.

In practice, this calculation is regularly reversed. Mass percents deserve to be identified experimentally via elemental analysis, and also these values deserve to be offered to calculation the empirical formula that unknown compounds. However, this information is inadequate to determine the molecular formula without added information ~ above the compound’s molecule weight.

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