Question

Which solution will have the lowest freezing point? 2.0 M sucrose 1.5 M NaCl 0.75 M MgCl2 2.0 M antifreeze

Answer 1

Depression in Freezing Point = i(vont hoff factor) * Kf * m

For surcose, vont hoff factor = 1 (non-electrolyte)

Depression in Freezing Point = 1 * Kf * 2 = 2 Kf

For NaCl, vont hoff factor = 2 (since it will dissociate into Na+ and Cl- ions)

Depression in Freezing point = 2 * Kf * 1.5 = 3 Kf

For MgCl2. vont hoff factor = 3(since it will dissociate into Mg(+2) and 2Cl- ions)

Depression in Freezing point = 3 * kf * 0.75 = 2.25 Kf

For antifreeze. vont hoff factor = 1(since it will not dissociate)

Depression in Freezing point = 1 * kf * 2= 2 Kf

Hence the lowest melting point will be of 1.5M NaCl solution