Question

Calculate the freezing point (Kf = 1.86 °C/m) of a 2.1m aqueous solution of KCl.

7.8 °C


3.9 °C


-7.8 °C


-3.9 °C

Answer 1

The freezing point of the solution is - 3.90 °C.

Step-by-step explanation:

• We can solve this problem using the relation:

ΔTf = (Kf)(m),

where, ΔTf is the depression in the freezing point.

Kf is the molal freezing point depression constant of water = - 1.86 °C/m,

m is the molality of the solution (m = 2.1 m).

∴ ΔTf = (Kf)(m) = (-1.86 °C/m)(2.1 m) = - 3.90 °C.

∵ The freezing point if water is 0.0 °C and it is depressed by - 3.90 °C.

∴ The freezing point of the solution is - 3.90 °C.