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Raoult's Law is a principle used to determine the vapor pressure of solutions. It states that the vapor pressure of a solution is the product of the mole fraction of the solvent and the vapor pressure of the pure solvent. In a formula, this law is expressed as \( P = P^\circ \times X_1 \). Here, \( P \) represents the vapor pressure of the solution, \( P^\circ \) is the vapor pressure of the pure solvent, and \( X_1 \) is the mole fraction of the solvent. This concept helps in understanding how a solute affects the boiling point and vapor pressure when dissolved in a solvent.
To utilize Raoult's Law, it's important to accurately find the mole fraction of the solvent. This involves comparing the vapor pressures (both measured and of the pure state). Note however, this applies to ideal solutions where interactions between molecules are similar to the solvent alone.

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure. For liquids like ethanol, knowing the boiling point is crucial in calculating changes when solutes dissolve in it. At the boiling point, liquids turn to vapor. When a solute is added, it causes the boiling point to elevate, requiring a higher temperature for boiling.
In our example, ethanol's normal boiling point at one atmosphere pressure is 78.4掳C, corresponding to a vapor pressure of 760 torr. Using Raoult's Law, the impact of adding non-volatile solute, such as the one in our problem, can be seen as it affects the solution's properties, increasing the boiling point.

Calculating molar mass is an essential part of chemistry. It helps determine the amount of substance needed or produced in a reaction. Molar mass is the mass of one mole of a given substance and is expressed in grams per mole (g/mol).
Following the steps, you use the molality derived from the mole fraction of the solute and the known mass of the solute. In the problem, the molar mass is found using the formula: Molar mass of solute = \( \frac{\text{mass of solute}}{\text{molality} \times \text{mass of solvent in kg}} \).

• The molality is found through the mole fractions calculated using Raoult's Law.
• Knowing the mass of the solute, you compute the molar mass.
• In our context, the molar mass calculation confirms the solute's properties and identity as 348 g/mol.

This highlights the interplay between vapor pressure, boiling point, and molecular composition.