Vp of aq soln of .1M glucose will b less than or greater thn .1M solution of glucose?

When considering the vapor pressure of a solution, it's essential to understand how solutes affect the properties of solvents. In the case of a 0.1 M glucose solution, the vapor pressure will be less than that of pure water or a pure solvent. This phenomenon is primarily due to the presence of solute particles in the solution.

Understanding Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase. For pure solvents, this pressure is determined by the temperature and the nature of the solvent. When a solute, like glucose, is added to a solvent, it disrupts the equilibrium between the liquid and vapor phases.

Raoult's Law

To explain why the vapor pressure of a 0.1 M glucose solution is lower, we can refer to Raoult's Law. This law states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent. Mathematically, it can be expressed as:

• P_solution = X_solvent * P°_solvent

Where:

• P_solution is the vapor pressure of the solution.
• X_solvent is the mole fraction of the solvent.
• P°_solvent is the vapor pressure of the pure solvent.

Impact of Glucose on Vapor Pressure

When glucose is dissolved in water, it occupies space that would otherwise be occupied by water molecules. This results in a decrease in the mole fraction of the solvent (water) in the solution. Since the vapor pressure is dependent on this mole fraction, the addition of glucose leads to a reduction in the overall vapor pressure of the solution compared to that of pure water.

Example for Clarity

Imagine you have a container filled with pure water. The water molecules at the surface can escape into the vapor phase, creating vapor pressure. Now, if you add glucose, the glucose molecules take up some of the space at the surface, meaning fewer water molecules can escape. As a result, the vapor pressure of the solution decreases.

Conclusion

In summary, the vapor pressure of a 0.1 M glucose solution will be less than that of pure water due to the presence of glucose molecules, which reduce the number of water molecules that can escape into the vapor phase. This principle is fundamental in understanding colligative properties, which describe how solute concentration affects the physical properties of solutions.