When a solute dissolves in a solvent, which of the following properties of the original solvent remains unchanged (if any)? Choose the best statement.

Introduction / Context:
Adding a solute to a solvent changes the solution’s properties relative to the pure solvent. Engineers must anticipate these changes to design separations, heat transfer operations, and reaction systems accurately.

Given Data / Assumptions:

• Dilute to moderate concentrations where colligative effects and transport-property changes are observable.
• Non-reactive solute unless stated otherwise.

Concept / Approach:
Key properties of the solvent are generally altered upon dissolution: vapor pressure decreases (Raoult’s law for nonvolatile solutes), boiling point elevates, freezing point depresses, viscosity and surface tension often change, and even specific heat of the resulting solution differs from that of the pure solvent. Therefore, the safest general statement is that none of these listed properties remain unchanged.

Step-by-Step Solution:

Verification / Alternative check:
Practical examples: adding salt to water lowers vapor pressure (hence boiling point elevation) and increases viscosity; adding sugar changes Cp and surface tension. Data tables confirm these trends.

Why Other Options Are Wrong:

• (a), (b), (c), (e): Each property is known to change upon dissolution in most real systems.

Common Pitfalls:
Assuming very dilute solutions behave identically to pure solvent; while changes may be small, they are generally nonzero and measurable.

Final Answer:
None of these