An aqueous CaCl2 solution has a vapor pressure of 82.5mmHg at 50 ∘C. The vapor pressure of pure water at this temperature is 92.6 mmHg. What is the concentration of CaCl2 in mass percent?

i worked this out with my professor earlier and he confused me when he divided the vapor pressure of CaCl2 (solute) by the vapor pressure of h2o (solution) sorry about the capitalizations, my keyboard is screwy. basically i thought to get a mole fraction you had to take the reactant under consideration and divide it by the total amount of moles or in this case vapor pressure of solution. Feed back is great

Question

An aqueous CaCl2 solution has a vapor pressure of 82.5mmHg at 50 ∘C. The vapor pressure of pure water at this temperature is 92.6 mmHg. What is the concentration of CaCl2 in mass percent?

i worked this out with my professor earlier and he confused me when he divided the vapor pressure of CaCl2 (solute) by the vapor pressure of h2o (solution) sorry about the capitalizations, my keyboard is screwy. basically i thought to get a mole fraction you had to take the reactant under consideration and divide it by the total amount of moles or in this case vapor pressure of solution. Feed back is great