# Applicatino of Raoults Law and melting point

• Grapz
In summary, the presence of an insoluble impurity, such as sodium sulfate, does not affect the melting point of an impure compound. This is because the impurity must be soluble in order to depress the melting point, and if it is insoluble, it is essentially equivalent to having only one compound present. Therefore, the vapor pressure and melting point will not be affected.
Grapz

## Homework Statement

What is the effect of an insoluble impurity such as sodium sulfate, on the observed melting point of a impure compound?

## The Attempt at a Solution

My answer is, there is no effect on the melting point of this particular compound. Because it has to be soluble in order to depress the melting point. If it is insoluble it is just like having 100 % of compound X and 0 % of compound Y, assuming there is only two compounds in this impure compound. Thus the vapor pressure is not effected and melting point will not change.

Is this a correct answer?

Grapz said:
Is this a correct answer?
Yes.

## 1. What is Raoults Law and how does it relate to the melting point of a substance?

Raoults Law states that the partial vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent multiplied by its mole fraction in the solution. This law is directly related to the melting point of a substance because as the vapor pressure of the solvent increases, the melting point decreases due to a decrease in the strength of intermolecular forces.

## 2. How is Raoults Law used in the determination of the melting point of a substance?

Raoults Law is used in the determination of the melting point of a substance by allowing us to calculate the mole fraction of the solvent in the solution using the partial vapor pressure and the vapor pressure of the pure solvent. This mole fraction can then be used to predict the melting point of the substance based on the relationship between vapor pressure and melting point.

## 3. Can Raoults Law be applied to all types of solutions?

No, Raoults Law is only applicable to ideal solutions, meaning that the molecules of the solute and solvent do not interact with each other and there is no change in the volume of the solution upon mixing. Real solutions can deviate from Raoults Law, especially at high concentrations or when there are strong intermolecular forces between the solute and solvent.

## 4. How can the application of Raoults Law be affected by external factors?

The application of Raoults Law can be affected by external factors such as changes in pressure and temperature. Changes in pressure can alter the vapor pressure of the solvent, while changes in temperature can affect the strength of intermolecular forces and thus the vapor pressure and melting point of the substance.

## 5. What are some practical applications of Raoults Law in scientific research?

Raoults Law is commonly used in scientific research to study the properties of solutions, such as determining the melting point of a substance, predicting the behavior of mixtures, and understanding the effects of different solvents on the properties of a solution. It is also utilized in industries such as pharmaceuticals and food processing to optimize processes and ensure product quality.

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