Determine the molar mass of the unknown solid. Is the unknown solid NaCO3,NaHCO3,NA3PO4, or KHC8H4O4?

Question

ok so, i have a mean prof who wants this worked out asap. if you could just give my the general walk through or hints to what i need to do, that would be awesome, i've read the chap and such still don't understand how. oh by that way this is what i am given thank you soooo much!
boiling pt of solute=89.0C,
H2O=100C,
M(unknown)=4.41g,
M(h2o)= 99.72g .
Kb(C/m)=.52(H2o)

NaCO3=105.99 g/mol
NaHCO3=84.008g/mol
NA3PO4=163.94g/mol
KHC8H4O4=116.22g/mol

Answer 1

I think you have mis-asked the question. I think that the boiling point of the unknown solute solution in water is 89.0C. This is a 11degC boiling point depression. From the boiling point depression, you have to work back to the molaltity of the unknown solute in the solution. The mass of solute in water is 4.41g. The mass of water is 99.72g. Molaltity is moles of solute in 1 kg (1000g) solvent (water). I think that Kb is degreesC/molal.