Percent Composition
Key Questions
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Percent composition tells you which types of atoms (elements) are present in a molecule and their levels. Percent composition can also tell you about the different elements present in an ionic compound as well.
Let's look at two examples
The molar mass of
#H_2O# is 18 g/mol
The hydrogens make up 2g (since each mole of hydrogen is 1g)
The oxygen makes up 16g.The percent composition of the compound is:
H = (2g/18g) x 100 = 11.1%
O = (16g/18g) x 100 = 88.9%Percent composition can be calculated the chemical formula of a compound, or it can be determined experimentally.
Here is a video which discusses how to calculate percent composition from experimental data for a reaction of iron and oxygen which produces an iron oxide compound.
Video from: Noel PaullerHope this helps!
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Here is an example for the compound C2HO4
You will first need to find the molar mass of the compound.
C = 2 x 12 = 24
O = 1 x 16 = 16
H = 4 x 1 = 4
Total mass = 40 amuTo find the percent composition you divide each part by the whole and multiply by 100 to convert to a %.
C = (24/44) x 100 = 54.5%
O = (16/44) x 100 = 36.4%
H = (4/44) x 100 = 9.1%Percent composition can also be calculated using experimental data. The video below shows you how to do that type of calculation.
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Percent composition in chemistry typically refers to the percent each element is of the compound's total mass.
The basic equation = mass of element / mass of compound X 100%
For instance, if you had a 80.0 g sample of a compound that was 20.0 g element X and 60.0 g element y then the percent composition of each element would be:
Element X = 20.0 g X / 80.0 g total x 100% = .250 or 25.0 %
Element Y = 60.0 g Y / 80.0 g total x 100 % = .750 or 75.0 %Here is a video which discusses how to calculate percent composition from experimental data for a reaction of iron and oxygen which produces an iron oxide compound. Video from: Noel Pauller