Solutions are made that contain 0.1 moles of each of the following compounds below in 100g of H20. Choose the compound whose solution will have the lowest freezing point?

NaBr
CO2
KClO3
MgCl2
MgSO4

delta T = i*Kf*m

i = 2 for NaBr
i = 1 for CO2
i = 2 for KClO3
i = 3 for MgCl2
i = 2 for MgSO4
i*m is the determining factor; you don't need to calculate the actual freezing point.

To determine which compound will have the lowest freezing point, we need to calculate the van't Hoff factor (i) for each compound. The van't Hoff factor accounts for the number of particles produced when a compound dissolves in a solvent.

The van't Hoff factor for ionic compounds like NaBr, KClO3, MgCl2, and MgSO4 can be calculated by determining the number of ions each compound dissociates into. For example, NaBr dissociates into one Na+ ion and one Br- ion, so its van't Hoff factor is 2. Similarly, KClO3 dissociates into one K+ ion and three ClO3- ions, so its van't Hoff factor is 4. MgCl2 dissociates into one Mg2+ ion and two Cl- ions, so its van't Hoff factor is 3. MgSO4 dissociates into one Mg2+ ion and one SO42- ion, so its van't Hoff factor is 2.

On the other hand, CO2 does not dissociate into ions when it dissolves in water. Instead, it remains as molecules, so its van't Hoff factor is 1.

The freezing point depression is directly proportional to the van't Hoff factor. Therefore, the compound with the highest van't Hoff factor will have the greatest freezing point depression and hence the lowest freezing point.

Based on the calculated van't Hoff factors:
- NaBr has a van't Hoff factor of 2
- CO2 has a van't Hoff factor of 1
- KClO3 has a van't Hoff factor of 4
- MgCl2 has a van't Hoff factor of 3
- MgSO4 has a van't Hoff factor of 2

As KClO3 has the highest van't Hoff factor of 4, it will have the greatest freezing point depression and therefore the lowest freezing point. Therefore, the compound with the lowest freezing point is KClO3.