As asked above, what is mole fraction solubility? From what I've been taught, it is the following equation: mole fraction solubility = (number of moles of solute)/(number of moles of solute + number of moles of solvent) Is that even correct? In actual fact, there's a question that deals with this problem. I've attached it for you to see. I've attempted it several times but I can't seem to reach the answer which is supposedly 8.98 x 10^-4 Many thanks.