Non-volatile solute

Definition

A non-volatile solute is a substance that does not readily evaporate and remains in a solution without contributing to the vapor pressure of that solution. The presence of a non-volatile solute affects the physical properties of the solvent, leading to phenomena such as lowering the vapor pressure, freezing point depression, and boiling point elevation, which are key aspects of colligative properties.

5 Must Know Facts For Your Next Test

1. Non-volatile solutes do not contribute to the vapor pressure of a solution, meaning their presence effectively reduces the overall vapor pressure compared to the pure solvent.
2. The degree to which a non-volatile solute lowers the vapor pressure can be quantified using Raoult's Law, which states that the vapor pressure of a solution is proportional to the mole fraction of the solvent.
3. When a non-volatile solute is dissolved in a solvent, it causes freezing point depression, meaning the freezing point of the solution is lower than that of the pure solvent.
4. Boiling point elevation occurs when a non-volatile solute is added to a solvent; this means that a higher temperature is required to reach the boiling point compared to the pure solvent.
5. Colligative properties, including those influenced by non-volatile solutes, are essential for understanding solutions in various applications such as antifreeze formulations and food preservation.

Review Questions

• How does the addition of a non-volatile solute affect the vapor pressure of a solvent?
  • When a non-volatile solute is added to a solvent, it reduces the vapor pressure of the solution compared to that of the pure solvent. This occurs because non-volatile solutes do not evaporate and therefore do not contribute to the vapor phase. The reduction in vapor pressure can be quantitatively described by Raoult's Law, which relates the vapor pressures to the mole fractions of the components in the solution.
• Discuss how colligative properties change with varying amounts of non-volatile solutes in a solution.
  • As more non-volatile solute is added to a solvent, colligative properties such as vapor pressure lowering, boiling point elevation, and freezing point depression become more pronounced. This means that with increasing concentration of non-volatile solute, the vapor pressure decreases further, the boiling point rises higher than that of the pure solvent, and the freezing point drops lower. These changes depend solely on the number of solute particles present rather than their chemical nature.
• Evaluate how understanding non-volatile solutes can impact real-world applications like food preservation and antifreeze solutions.
  • Understanding non-volatile solutes is crucial for practical applications such as food preservation and antifreeze formulations. In food preservation, adding non-volatile solutes can lower freezing points and prevent ice crystal formation, thereby maintaining texture and quality. Similarly, in antifreeze solutions, non-volatile solutes raise the boiling point and lower the freezing point of water, allowing automotive cooling systems to operate effectively in extreme temperatures. This knowledge helps in designing effective products for maintaining stability and safety in diverse environments.

Related terms

vapor pressure:

The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature.

colligative properties:

Properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute.

boiling point elevation:

The phenomenon where the boiling point of a solvent increases when a non-volatile solute is added, requiring more energy to achieve boiling.