Solutions

mole fraction

Mole fraction is the number of moles of a substance divided by the total number of moles in the solution.

Mole Fraction =	moles of substance A
	Total Moles of solution

Example:

If there is 4.0 moles of HCl in 12 moles of solution then the mole fraction of HCl would be 1/3. When all mole fractions are added together the total is always 1.