Mole fraction

Mole fraction is a way of expressing composition purely in terms of the relative number of moles of each component in a solution, ignoring their masses or volumes altogether. It is defined, for any one component, as the ratio of the number of moles of that particular component to the total number of moles of every component present in the solution. If a substance A dissolves in a substance B, and their amounts are $n_A$ and $n_B$ moles respectively, then the mole fraction of A is $x_A = \dfrac{n_A}{n_A + n_B}$ and the mole fraction of B is $x_B = \dfrac{n_B}{n_A + n_B}$. By this definition, the mole fractions of every component in a solution must always add up to exactly 1, since together they account for the e …