Chemistry Practice Problems Freezing Point Depression Practice Problems Solution: What is the freezing point of an aqueous solution ...

Solution: What is the freezing point of an aqueous solution that boils at 104.6 °C?

Problem

What is the freezing point of an aqueous solution that boils at 104.6 °C?

Solution

We have to calculate the freezing point of an aqueous solution that boils at 104.6 °C.


When a nonvolatile solute is dissolved in a solvent, the freezing point of the resulting solution is always lower than the freezing point of pure solvent. This property of solutions is called the freezing point depression.

The formula for freezing point depression is:

Tf = i·Kf·m

Where,

ΔTf = change in freezing point

i = van ‘t Hoff constant (i = 1 for nonelectrolytes)

Kf =freezing point depression constant

m = molality of solution


When a nonvolatile solute is dissolved in a solvent, the boiling point of the resulting solution is always higher than the boiling point of pure solvent. This property of solutions is called the boiling point elevation.

The formula for boiling point elevation is:

Tb = i·Kb·m

Where,

ΔTb = change in boiling point

i = van ‘t Hoff constant (i = 1 for nonelectrolytes)

Kb = boiling point elevation constant

m = molality of solution

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