Which Aqueous Solution Has The Lowest Vapor Pressure

In chemistry, vapor pressure refers to the pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature. A lower vapor pressure indicates a higher stability of the liquid phase since fewer molecules are escaping into the vapor phase. In the context of aqueous solutions, the vapor pressure is influenced by the presence of solutes in the water. In this article, we will explore which aqueous solution has the lowest vapor pressure and the factors that contribute to this phenomenon.

Factors Affecting Vapor Pressure of Aqueous Solutions

The vapor pressure of an aqueous solution is influenced by several factors:

  • Solute concentration: The presence of solutes in water reduces the vapor pressure of the solution compared to pure water.
  • Nature of the solute: The type of solute and its interaction with water molecules can impact the vapor pressure of the solution.
  • Temperature: Vapor pressure increases with temperature, so the temperature of the solution is a critical factor in determining its vapor pressure.
  • Vapor pressure lowering: This phenomenon is also known as Raoult’s Law, which states that the vapor pressure of a solution is directly proportional to the mole fraction of solvent present in the solution. As a result, the addition of solutes lowers the vapor pressure of the solution.

Which Aqueous Solution Has The Lowest Vapor Pressure?

Considering the factors mentioned above, the aqueous solution with the lowest vapor pressure is the one with the highest concentration of non-volatile solutes. This phenomenon is explained by the colligative properties of solutions, where the presence of solutes affects the physical properties of the solvent.

Key points to consider:

  • The lower the vapor pressure, the greater the stability of the solution.
  • Higher solute concentration leads to a lower vapor pressure in the solution.
  • Non-volatile solutes have a significant impact on lowering the vapor pressure of aqueous solutions.

Examples of Aqueous Solutions with Low Vapor Pressure

Several common examples illustrate the concept of aqueous solutions with low vapor pressure:

SolutionNon-volatile Solute
SaltwaterNaCl (table salt)
Sugar solutionC12H22O11 (sucrose)
Antifreeze solutionethylene glycol

These solutions contain non-volatile solutes that significantly reduce the vapor pressure of the water component, making them suitable for various applications in chemistry, biology, and industry.

FAQs About Vapor Pressure of Aqueous Solutions

1. How does the presence of non-volatile solutes affect the vapor pressure of an aqueous solution?

When non-volatile solutes are added to water, the escaping tendency of water molecules into the vapor phase is reduced, resulting in a lower vapor pressure for the solution compared to pure water.

2. Why does a higher solute concentration lead to a lower vapor pressure in the solution?

According to Raoult’s Law, the vapor pressure of a solution is directly proportional to the mole fraction of the solvent. Therefore, a higher solute concentration leads to a lower mole fraction of the solvent, reducing the vapor pressure of the solution.

3. Can the nature of the solute impact the vapor pressure of an aqueous solution?

Yes, the nature of the solute can affect its interaction with water molecules, leading to different degrees of vapor pressure reduction in the solution. Non-volatile solutes tend to have a more significant impact on lowering vapor pressure compared to volatile solutes.

4. How does temperature influence the vapor pressure of an aqueous solution?

As the temperature of the solution increases, the vapor pressure also increases. Higher temperatures promote the escape of molecules into the vapor phase, leading to a higher vapor pressure in the solution.

By understanding the factors that contribute to the vapor pressure of aqueous solutions and recognizing the impact of non-volatile solutes, we can appreciate the significance of low vapor pressure in various practical applications. Whether in chemical reactions, biological processes, or industrial processes, the concept of vapor pressure in solutions plays a crucial role in understanding their behavior and properties.

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