Which of the following aqueous solutions has the lowest freezing point?
a: 1.0 m ionic nacl
b: 1.0 m ionic mgbr2
c: 1.0 m molecular c12h22o11
d: 1.0 m ionic lif

Option B: ionic Mg Br2.

Because the depression of freezing point is proportional to the number of moles of solute per kg of solvent, and given that 1 mol Mg Br2 dissociates into three moles of ions, the solution of Mg Br2 will have more moles of particles and exhibit the largest reduction in the freezing point.