Question

When 2.36g of a nonvolatile solute is dissolved in 100g of solvent, the largest change in freezing point will be achieved when the solvent is
A. paradichlorobenzene, kf=7.10.
B. water, Kf=1.86.
C. tert-butanol, Kf=9.1.
D All are expected to have the same freezing point.

Answer 1

Answer:

Option c → Tert-butanol

Explanation:

To solve this, you have to apply the concept of colligative property. In this case, freezing point depression.

The formula is:

ΔT = Kf . m . i

When we add particles of a certain solute, temperature of freezing of a solution will be lower thant the pure solvent.

i = Van't Hoff factor (ions particles that are dissolved in the solution)

At this case, the solute is nonvolatile, so i values 1.

ΔT = Difference between  fussion T° of pure solvent - fussion T° of solution.

T° fussion paradichlorobenzene = 56 °C

T° fussion water = 0°

T° fussion tert-butanol = 25°

Water has the lowest fussion temperature and the paradichlorobenzene has the highest Kf. But the the terbutanol, has the highest Kf so this solvent will have the largest change in freezing point, when all the molalities are the same.