In homogenous solution, solute and solvent are present in one phase such that both cannot be distinguished or easily separated. Mole fraction of both solute and solvent of a homogenous mixture is unity or 1.

$\text{ X solute }+\mathrm{X}\text{ solvent }=\frac{{\mathrm{n}}_{\text{solute }}}{{\mathrm{n}}_{\text{solute }}+{\mathrm{n}}_{\text{solvent }}}+\frac{{\mathrm{n}}_{\text{solvent }}}{{\mathrm{n}}_{\text{solute }}+{\mathrm{n}}_{\text{solvent }}}=1$