The solute that raises the boiling point of water the most is the one with the highest molality and the highest van't Hoff factor (i).

Here's why:

* Molality: Molality is the number of moles of solute per kilogram of solvent. The more solute you dissolve, the greater the effect on the boiling point.

* van't Hoff factor (i): This factor represents the number of particles a solute dissociates into when dissolved in a solvent. For example:

* NaCl: Dissociates into Na+ and Cl- ions, so i = 2.

* Sugar (C12H22O11): Does not dissociate, so i = 1.

* CaCl2: Dissociates into Ca2+ and 2Cl- ions, so i = 3.

Therefore, a solution with a high molality of a solute that dissociates into many particles (high i) will have the largest increase in boiling point.

Example: A 1 molal solution of CaCl2 would raise the boiling point of water more than a 1 molal solution of NaCl, because CaCl2 dissociates into more particles (i=3) compared to NaCl (i=2).

Note: The specific boiling point elevation is determined by the molality and the molal boiling point elevation constant (Kb) of the solvent.