Q:
# What Is the Molal Freezing Point Depression Constant?

Freezing point depression represents the variation in the freezing temperature of a pure solvent from that of the solvent in solution. In the equation ΔT=Kf m i, where i is the van’t Hoff factor, Kf represents the molal freezing point depression constant, also called the cryoscopic constant.

Continue ReadingThe change in the freezing temperature of pure solvent from that of its solution is calculated by using two constants. These are multiplied by the molality of the solution in moles per kilogram. In the relevant equation, ΔT represents the change in freezing temperature of the pure solvent from that of the solution, and m represents the molal concentration of the solution.

This concept is easily demonstrable by working an example. Take a solution of 1.6g of naphthalene dissolved in 20g of benzene. The freezing point of pure benzene is 5.5 degrees Celsius and that of the mixture is 2.8 degrees Celsius. It is therefore possible to calculate the Kf of the solution as follows:

ΔT is 5.5 - 2.8 = 2.7 degrees Celsius.

Moles of Naphthalene in solution = (1.6) (1/128) = 0.0125.

Therefore, the molality of the solution is 0.0125 mol / 0.02 kg = 0.625 m.

Per the equation, 2.7= (Kf) (0.625m); therefore, Kf= (2.7)/(0.625).

In this example, the molal freezing point depression constant for the solution equals 4.3 degrees Celsius/m.

Learn more about States of Matter-
Q:
## What Is the Difference Between Celsius and Centigrade?

A: The difference between Celsius and centigrade lies in the 0.01 degree variation that exists between the triple point of water in each scale. The Celsius sc... Full Answer >Filed Under: -
Q:
## What Is the Enthalpy of Solution?

A: The enthalpy of solution refers to the temperature changes in a solution when a substance dissolves in the solvent. There can be positive or negative react... Full Answer >Filed Under: -
Q:
## What Is the Freezing Point of Water in Fahrenheit?

A: On the Fahrenheit temperature scale, the freezing point of water is 32 degrees. Fahrenheit observed this by placing a thermometer in an equal mixture of wa... Full Answer >Filed Under: -
Q:
## What Is the Freezing Point of Iron?

A: The freezing point of iron, which is the same as its melting point, is 2800 degrees Fahrenheit. Iron has a boiling point of 5182 degrees Fahrenheit. Iron i... Full Answer >Filed Under: