What will be the freezing point of a solution

Colligative properties are properties that differ based on the concentration of solute in a solvent, but not on the type of solute. What this means for the example above is that people in colder climates do not necessarily need salt to get the same effect on the roads—any solute will work. However, the higher the concentration of solute, the more these properties will change. When table salt is added to water, the resulting solution has a higher boiling point than the water did by itself.

The ions form an attraction with the solvent particles that prevents the water molecules from going into the gas phase. This is true for any solute added to a solvent; the boiling point will be higher than the boiling point of the pure solvent without the solute.

In other words, when anything is dissolved in water, the solution will boil at a higher temperature than pure water would. The boiling point elevation due to the presence of a solute is also a colligative property. That is, the amount of change in the boiling point is related to the number of particles of solute in a solution and is not related to the chemical composition of the solute. The effect of adding a solute to a solvent has the opposite effect on the freezing point of a solution as it does on the boiling point.

A solution will have a lower freezing point than a pure solvent. The freezing point is the temperature at which the liquid changes to a solid. At a given temperature, if a substance is added to a solvent such as water , the solute-solvent interactions prevent the solvent from going into the solid phase. The solute-solvent interactions require the temperature to decrease further in order to solidify the solution. A common example is found when salt is used on icy roadways.

The de-icing of planes is another common example of freezing point depression in action. A number of solutions are used, but commonly a solution such as ethylene glycol, or a less toxic monopropylene glycol, is used to de-ice an aircraft. The aircrafts are sprayed with the solution when the temperature is predicted to drop below the freezing point.

The freezing point depression is the difference in the freezing points of the solution from the pure solvent. This is true for any solute added to a solvent; the freezing point of the solution will be lower than the freezing point of the pure solvent without the solute.

Thus, when anything is dissolved in water, the solution will freeze at a lower temperature than pure water would. The freezing point depression due to the presence of a solute is also a colligative property.

That is, the amount of change in the freezing point is related to the number of particles of solute in a solution and is not related to the chemical composition of the solute. Recall that covalent and ionic compounds do not dissolve in the same way. The new freezing point of water, which is normally 0 o C, is equal to: 0 — 0. Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:.

Skip to main content. Search for:. Freezing Point Depression. Learning Objective Discuss the effects of a solute on the freezing point of a solvent.

Key Points The freezing point depression can be calculated using the pure solvent freezing point and the molality of the solution. Be careful not to use the mass of the entire solution. Often, the problem will give you the change in temperature and the proportionality constant, and you must find the molality first in order to get your final answer.

The solute, in order for it to exert any change on colligative properties, must fulfill two conditions. First, it must not contribute to the vapor pressure of the solution, and second, it must remain suspended in the solution even during phase changes.

Because the solvent is no longer pure with the addition of solutes, we can say that the chemical potential of the solvent is lower. Chemical potential is the molar Gibb's energy that one mole of solvent is able to contribute to a mixture. The higher the chemical potential of a solvent is, the more it is able to drive the reaction forward. Consequently, solvents with higher chemical potentials will also have higher vapor pressures. The boiling point is reached when the chemical potential of the pure solvent, a liquid, reaches that of the chemical potential of pure vapor.

Because of the decrease in the chemical potential of mixed solvents and solutes, we observe this intersection at higher temperatures. In other words, the boiling point of the impure solvent will be at a higher temperature than that of the pure liquid solvent. Thus, boiling point elevation occurs with a temperature increase that is quantified using. Freezing point is reached when the chemical potential of the pure liquid solvent reaches that of the pure solid solvent.

Again, since we are dealing with mixtures with decreased chemical potential, we expect the freezing point to change. Unlike the boiling point, the chemical potential of the impure solvent requires a colder temperature for it to reach the chemical potential of the pure solid solvent. Therefore, a freezing point depression is observed. What is the molar mass of the compound?