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Mass Transfer - Engineering

Q1:

Raoult's law applies to the

A all liquid solutions

B non-ideal solution only.

C non-volatile solute.

D solvents.

ANS:D - solvents.

Certainly! In the context of Raoult's law, "solvents" refer to the substances that act as the predominant component in a solution, dissolving the solute. Here's an explanation:

  1. Solvent:
    • A solvent is a substance that has the ability to dissolve other substances, known as solutes, to form a homogeneous mixture called a solution.
    • In a solution, the solvent is present in a larger quantity compared to the solute. It provides the medium in which the solute is dispersed or dissolved.
    • Solvents are often liquids, but they can also be gases or solids depending on the system. Common examples of solvents include water, alcohol, acetone, and various organic solvents.
    • The choice of solvent depends on factors such as the nature of the solute, the desired properties of the solution, and the intended application.
  2. Role in Raoult's Law:
    • In the context of Raoult's law, which applies to ideal liquid solutions, the solvent is typically the component whose vapor pressure is used in the calculations.
    • Raoult's law states that the partial vapor pressure of each component in an ideal liquid solution is directly proportional to its mole fraction in the solution, multiplied by the vapor pressure of the pure component.
    • The solvent's vapor pressure is crucial in determining the behavior of the solution according to Raoult's law, as it influences the partial vapor pressures of both the solvent and the solute.
  3. Example:
    • For example, in a solution of ethanol (C2H5OH) and water (H2O), where ethanol is the solute and water is the solvent, Raoult's law would describe the relationship between the partial vapor pressures of ethanol and water in the solution based on their respective mole fractions and vapor pressures.
In summary, in the context of Raoult's law and solutions, "solvents" are the substances that serve as the predominant component, dissolving the solute, and their properties, particularly their vapor pressures, play a significant role in determining the behavior of the solution.