Question

The sum of mole fractions of solute and solvent of a solution is equal to :

• A. number of moles of solute
• B. number of moles of solvent
• C. number of moles of solution
• D. unity

Answer 1

The correct option is D unity

Let mole fractions of A, B in a binary solution be $X_A$ and $X_B$ respectively.

$X_A=\frac{n_A}{n_A+n_B}$

$X_B=\frac{n_B}{n_A+n_B}$

$\therefore X_A+X_B=\frac{n_A+n_B}{n_A+n_B}=1$