Learning ObjectiveTranslate between a molecular formula of a compound and its percent complace by mass
Key PointsThe atomic complace of chemical compounds have the right to be explained in a range of means, including molecular formulas and also percent complace.The percent complace of a compound is calculated through the molecular formula: divide the mass of each aspect discovered in one mole of the compound by the total molar mass of the compound.The percent composition of a compound have the right to be measured experimentally, and these values can be supplied to recognize the empirical formula of a compound.

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Termpercent by massThe fraction, by weight, of one facet of a compound.

The atomic complace of chemical compounds deserve to be described utilizing a variety of notations consisting of molecular, empirical, and structural formulas. Another convenient way to explain atomic composition is to research the percent complace of a compound by mass.

Percent Complace by Mass

Percent composition is calculated from a molecular formula by splitting the mass of a single aspect in one mole of a compound by the mass of one mole of the entire compound. This worth is presented as a portion.

Percentage Composition – YouTubeThis video mirrors just how to calculate the percent composition of a compound.

For instance, butane has a molecular formula of C4H10. Butane’s percent complace can be calculated as follows:

Mass of H per mol butane: 10:mol:H cdot frac1.00794:g1:mol: H = 10.079:g:HMass of C per 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

Thus, the atomic complace of butane have the right to also be explained as 17.3% hydrogen and 82.7% carbon, and, as supposed, these values sum to 100%.

ButaneThe structural formula of butane.

In exercise, this calculation is often reversed. Mass percents have the right to be determined experimentally via elemental analysis, and also these values can be used to calculate the empirical formula of unknown compounds. However, this indevelopment is inadequate to recognize the molecular formula without added indevelopment on the compound’s molecular weight.

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