Question

From the results of Experiment \(2,\) what would one hypothesize, if anything, about the effect of the number of solute particles dissolved in \(\mathrm{H}_{2} \mathrm{O}\) on the boiling point of a solution? A. The more solute particles that are present, the higher the boiling point. B. The more solute particles that are present, the lower the boiling point. C. No hypothesis can be made because only 1 solute was tested. D. The number of solute particles produced does not affect the boiling point.

Short answer

Answer: The more solute particles that are present, the higher the boiling point.

Step-by-step solution

Understand boiling point elevation

Boiling point elevation is a phenomenon in which the boiling point of a solvent increases when a non-volatile solute is added to it. This phenomenon is explained by the concept of vapor pressure lowering in presence of a solute.

Identify the relationship between solute particles and boiling point elevation

The more solute particles dissolved in a solvent like water, the more significant the boiling point elevation becomes. Colligative properties, including boiling point elevation, depend on the number of solute particles (molecules or ions) present in the solution, not their nature or identity. If the concentration of solute particles increases, the rate of vaporization in water decreases, causing the boiling point to elevate.

Analyze the given options and select the right answer

Based on our understanding of boiling point elevation and the relation between solute particles and boiling point, we can analyze the given options: A. The more solute particles that are present, the higher the boiling point: This option is consistent with the concept of boiling point elevation due to the presence of solute particles. B. The more solute particles that are present, the lower the boiling point: This option contradicts the concept of boiling point elevation. C. No hypothesis can be made because only 1 solute was tested: As colligative properties depend on solute concentration rather than the type of solute, this option is not valid. D. The number of solute particles produced does not affect the boiling point: This option also contradicts the concept of boiling point elevation. Considering the right understanding of boiling point elevation, the most plausible hypothesis among the given options is: A. The more solute particles that are present, the higher the boiling point.

Key concepts

Colligative Properties

Colligative properties are a group of properties in solutions that depend on the number of solute particles relative to the number of solvent molecules, rather than the type of solute particles. This concept is particularly relevant when discussing boiling point elevation, a key colligative property.

These properties are vital to understanding how adding different substances can change the physical characteristics of a solution. In the context of your textbook exercise, boiling point elevation illustrates how, when a non-volatile solute is dissolved in water, it disrupts the escape of water molecules into the gas phase, resulting in a need for more heat to reach the boiling point. Thus, the more solute particles present, the higher the boiling temperature of the solution, as more energy is required to overcome the additional intermolecular attractions caused by the solute particles.

Key Takeaways:

• Colligative properties focus on particle count, not type.
• Boiling point elevation is one such property.
• The physical characteristics of a solution change with the addition of a solute.

Vapor Pressure Lowering

Vapor pressure lowering is closely tied to colligative properties and is another key player in how solutes affect boiling points. The vapor pressure of a liquid is the pressure exerted by its vapor when the liquid and vapor phases are in dynamic equilibrium. Essentially, it's a measure of a liquid's tendency to evaporate.

When a solute is dissolved in a solvent, the vapor pressure of the solvent decreases because the solute particles occupy space at the surface of the liquid, hindering the escape of solvent molecules into the vapor phase. This results in fewer solvent molecules being able to escape, thus lowering the vapor pressure. Since boiling occurs when vapor pressure equals atmospheric pressure, a solution with lower vapor pressure requires more heat to reach that point—hence, a higher boiling point.

Important Points:

• Vapor pressure is a measure of a liquid's propensity to turn into vapor.
• Solute particles decrease the solvent's vapor pressure.
• Lower vapor pressure leads to higher boiling point.

Solute Concentration

Solute concentration is the amount of solute present in a given quantity of solution or solvent. It has a direct influence on the magnitude of colligative properties including boiling point elevation. In the context of the exercise, increasing the number of solute particles will proportionally elevate the boiling point of the water.

The relationship between solute concentration and boiling point is a cornerstone of thermodynamics in chemistry. With each additional solute particle, there's a greater disruption of the solvent's natural properties. Hence, a solution with a high concentration of non-volatile solute will have a much higher boiling point than that of the pure solvent.

Essentials to Remember:

• Solute concentration is measured by the amount of solute in a solution.
• Greater solute concentration usually leads to significant elevation in boiling point.
• The link between solute concentration and boiling point is foundational in understanding solutions.