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# Law of Definite Proportions

## Compounds contain the same elements in the same proportion by mass.

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Law of Definite Proportions

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The law of definite proportions states that a chemical compound always contains the same proportion of elements by mass, that the make-up of the compound is fixed.

Knowing this, how do you calculate definite proportions?

One way is to find the molar mass of the compound, and the mass of the each constituent part of the compound within one mole of the compound. Then, simply divide the mass of each component by the total mass.

Using this method, in what proportions by mass do Carbon and Oxygen combine to form CO2?