Question

When a solute is added to a solvent, the freezing point of the solution is

a. higher than the freezing point of either substance alone.
b. lower than the freezing point of either substance alone.
c. the same as the freezing point of the solute.
d. the same as the freezing point of the solvent?

Answer 1

Answer: The correct answer is Option b.

Step-by-step explanation:

Freezing point of a substance is defined as the temperature at which the solid and the liquid forms of a substance are in equilibrium. This means that the solid and liquid forms of a substance have the same vapor pressure.

It is observed that the freezing point of the solution is always lower than the pure solvent. Decreasing the vapor pressure of liquid is done by adding some solute particles to the solution. This decrease is called as depression in freezing point.

The expression for the depression in freezing point is given as:

`\Delta T_f=K_f* m`

where,

`\Delta T_f` = depression in freezing point

`K_f` = Cryoscopic constant

m = molality of the solution

Hence, the correct answer is Option b.

Answer 2

It is lower than the freezing point of either substance alone. The freezing points of solutions are observed to be all lower than that of the solvent alone since there will be more particles present in the solution. The solute particles will block the crystallization of the solution and hence there will be a depression in the freezing point of the solution.