Question

For a 0.50 molal solution of sucrose in water, calculate the freezing point and the boiling point of the solution. Please list each step.

Answer 1

We can solve for the freezing point and the boiling point of the solutions by using the freezing point depression and boiling point elevation formulas.

ΔTb = Kb m i

ΔTf = Kf m i

where,

Kb and Kf are the boiling point and freezing point constants for water

Kb = 0.51 °C / molal

Kf = - 1.86 °C / molal

m = molality = 0.50 molal

i = vant Hoff factor = 1

The freezing point and boiling points are:

Freezing point = 0°C + ΔTf

Freezing point = 0°C + (-1.86 °C / molal * 0.5 molal)

Freezing point = - 0.93 °C

Boiling point = 100°C + ΔTb

Boiling point = 100°C + (0.51 °C / molal * 0.5 molal)

Boiling point = 100.255°C