Depression of freezing point is given by the equation:
ΔTf = m. Kf. i
where i is the Van't Hoff factor, m is the molality, and Kf is the freezing point depression constant.
As per the formula, depression of freezing point is directly proportional to the molality. 2.0 m NaCl has the highest molaity and will have the maximum depression in freezing point. As a result it will also have the lowest freezing point.
