Question

The law of relative lowering of vapour pressure was given by:

• A. Raoult
• B. Ostwald
• C. Henry
• D. Van’t Hoff

Answer 1

The Correct Option is A

To solve the question regarding the principle of "relative lowering of vapor pressure," we need to identify the scientist who formulated and described this concept in the context of solutions.

1. Concept Understanding: The law of relative lowering of vapor pressure is a fundamental principle in physical chemistry. It states that the relative lowering of vapor pressure of a solvent, when a non-volatile solute is dissolved into it, is equal to the mole fraction of the solute in the solution.
2. Mathematical Representation: The law can be expressed as: \[\frac{{P_0 - P}}{{P_0}} = \text{{X}}_{\text{{solute}}}\] where \( P_0 \) is the vapor pressure of the pure solvent, \( P \) is the vapor pressure of the solvent after adding the solute, and \( \text{{X}}_{\text{{solute}}} \) is the mole fraction of the solute.
3. Scientist Behind the Law: This law was given by the French chemist François-Marie Raoult. Raoult's laws describe the properties of ideal solutions, establishing foundational principles in solution chemistry.
4. Option Analysis:
   • Raoult: Correct answer as the principle was coined by François Raoult.
   • Ostwald: He is known for Ostwald's dilution law and contributions to catalysis, not for the vapor pressure concept.
   • Henry: Known for Henry's law concerning gas solubility in liquids, not vapor pressure lowering.
   • Van’t Hoff: Recognized for work on osmotic pressure and chemical reaction dynamics, not specifically for vapor pressure.

In conclusion, the law of relative lowering of vapor pressure was given by Raoult, which is the correct answer.