An aqueous CaCl_2 solution has a vapor pressure of 82.1mmHg at 50C. The vapor pressure of pure water at this temperature is 92.6mmHg.

Question

What is the concentration of CaCl_2 in mass percent?

Answer 1

I would approach the problem this way.
You know P_solvent = X_{solvent</sub*P^osolvent. This allows you to determine Xsolvent. Now you have X for solvent and X for CaCl2. Convert those to grams and to mass percent.
Can you take it from here?}

Answer 2

43.2%