Re: Do all solutes lower the freezing temperature of water?

Yes. The formula is:

Delta Tf = i Kf m 

where: 

Delta Tf = change in freezing point for the solvent in the solution 

i = Van't Hoff factor (which will be 1 if the solute is a non-electrolyte) 

Kf = Freezing Point Depression Constant 

m = concentration in moles of solute per kilogram of solvent

     assuming that putting quotes around the word solute doesn't make it 
mean something else. What do I mean? If something is soluble, then it is 
a solute. If something isn't soluble, then it's not a solute. A dispersion 
of something insoluble (e.g. vegetable oil in water, or water in mercury) 
doesn't act the same way because it's not a solution. Soluble oils used in 
anti-rust additives are called that because they are soluble at the levels 
used in the formulation.