An aqueous CaCl2 solution has a vapor pressure of 81.6 mmHg 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? (Assume complete dissociation of the solute.)

Video transcript

Hi everyone here we have a question telling us that a solution of fructose and acetone has a vapor pressure of 204.0 millimeters of mercury at 25.0 degrees Celsius. And our goal here is to calculate the mass percent of fruit toast in the solution. Acetone has a vapor pressure of 231.0 millimeters of mercury at 25.0 degrees Celsius. So we're gonna use the formula. The pressure of the solution equals the mass fraction of the solution times the pressure of the solvent. So the mass fraction of the solvent equals the pressure of the solution, divided by the pressure of the solvent, Which means zero of Mercury Divided by 231. mm of Mercury Equals 0.8831. Now we're going to use the mole fraction of the solvent equals the end of the solvent, divided by the end of the salute plus in of solvent. So we're going to assume that we have one mole of the solvent. So 0. equals one mole divided by in a salute plus one mole. So 0. times in a salute plus one mole equals one mole in of salute Equals 0.1169 moles Divided by 0. equals 0.13 to four moles, calculating the mass of solute and solvent salute equals fructose Equals .16 g per mole. The mass of the salute equals 0.13 to four moles times 180. g Divided by one Mole. And our mole's here are canceling out and that equals 23.85 g. Our solvent equals acetone And it has .08 g per mole. So the mass of our solvent equals one mole Times 58.08 g over one mole. And our mole's here are canceling out, and that equals 58. g. So our mass percent equals the mass of the salute, divided by the mass a salute plus solvent times 100. So our mass percent equals 23.85g, Divided by 23.85 g Plus 58.08 g. Times Equals 29.11%. And that is our final answer. Thank you for watching. Bye.