The new vapor pressure of a solution of 3.25g of an unknown compound in 22.35g of H2O is 114.9mmHg at 55 degrees Celcius. What is the molar mass of the unknown compound?

Answer 1

Note the correct spelling of celsius.

Psoln = XH2O*Pnormal
Substitute for Psoln 114.9, look up vapor pressure of H2O at 55 C and substitute for Pnormal, solve for XH2O.

Then
moles H2O/(moles H2O+moles unknown) = XH2O from above.
Substitute moles H2O (from grams/molar mass) and solve for moles unknown.

You know moles = grams/molar mass. You know grams and moles, solve for molar mass.