We’re being asked to determine the mass percent of CaCl2 in solution. Recall that the mass percent of a solution is given by:
We’re given the vapor pressure of the solution, 106.4 mmHg, and the vapor pressure of pure water, 118.0 mmHg. The vapor pressure of a solution can be given by Raoult’s Law:
where P˚ = vapor pressure of solvent and χ = mole fraction of solvent. This means that for this solution:
The mole fraction of H2O is:
An aqueous CaCl2 solution has a vapor pressure of 106.4 mmHg at 55.0 oC. The vapor pressure of pure water at this temperature is 118.0 mmHg. What is the concentration of CaCl2 in mass percent?
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