Mass fraction (chemistry)

In general, the mass fraction (symbol: ω or y or ξ, often simplified to w ), formerly also mass fraction of a component in a mixture, the relative mass of the component in the total mass of the mixture. He is thus one of the content information.

Definition and calculation

Calculated the mass fraction at the breaking out of the mass of the component by the total mass of the mixture.

Wherein:

With n components:

The mass fraction is thus a measure of the fractional mass of a component in a mixture and is mainly used in Tw - phase diagrams using. If the mass fraction 1 is the respective component in its pure form, it is 0, it is not included in the mixture.

Multiplying the mass fraction of 100 %, so it can also be in the form of percentage Specify size; these are sometimes still not DIN wordings weight percent ( Abbr: wt - %) and percent by mass (abbreviation: Ma % m or %) to be found.

Since such a measure is very versatile, arising from his numerous applications in various fields, particularly chemistry ( mixed phase ), but also the mineralogy, petrology, materials science and materials science, for example, the composition of rocks, minerals (mixed crystal) and alloys to describe.

Solutions

For the example of a solution is calculated, the respective mass fraction of the solvent and the dissolved components as follows:

At n dissolved components:

For approximate calculations, it is assumed simplified in the special case that the mass fraction of the component in relation to the solution is negligibly small and therefore you can set the mass fraction of the solution is equal to 1.

The mass fraction of a component in a solution is the ratio between the mass concentration of this component in dissolved form (partial density of this component ) and the density of the solution. This can be demonstrated by replacing the bulk of the solution in the definition of the mass fraction of the product of the density and volume of the solution, and applying the definition of the mass concentration (ratio of the mass of the ingredient and the volume of the solution).