Mass Fraction of Element

The mass fraction calculator finds what part of the mass of a compound is made up by the chosen element and shows the fractions of all elements. The second mode finds the mass of an element in a sample: for example, how much iron 100 kg of Fe₂O₃ contains.

Mass fraction formula

w(E) = ^{n · A_r(E)}/_Mr(compound) · 100 %

n is the number of atoms of the element in the formula, A_r is its relative atomic mass and M_r is the relative molecular mass of the compound. The mass fractions of all elements add up to 100 %.

Mass of an element in a sample

m(E) = w(E) · m(compound)

Example 1. w(Fe) in Fe₂O₃ = 2 · 56 / 160 · 100 % = 70 %.

Example 2. 100 kg of Fe₂O₃ contains 0.7 · 100 = 70 kg of iron.