Mass fraction (chemistry).html

In chemistry the mass fraction is the fraction of one substance ( $x A$ ) with mass $m A$ to the total mixture mass $m t o t$ would be defined as:

$x_A = \frac {m_A}{m_{tot}}$

with the sum of all the mass fractions equal to 1:

$\sum_{i=1}^{N} m_i = m_{tot} ; \sum_{i=1}^{N} x_i = 1$

It is a way of expressing concentration in a dimensionless size. Multiplying by 100 obtains the mass percentage. The mass fraction of component in a solution is the ratio between the mass concentration of that component in solution ρ_A (partial density of that component) and the density of solution ρ. This can be proved by replacing the mass of solution from the definition of mass fraction by the product between the density and the volume of solution and applying the definition of mass concentration (ratio between mass of the component and the volume of solution).

Mass fraction (chemistry).html

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See also