Question

The law of the relative lowering or vapour pressure was given by (a) van't Hoff (b) Ostwald (c) Raoult (d) Henry

Short answer

The correct answer is (c) Raoult

Step-by-step solution

Recognize the Law and its Contributor

In this case, it is important to know that 'Law of relative lowering of vapour pressure' is also known as Raoult's law. So, the corresponding scientist is Raoult.

Key concepts

Vapour Pressure

Vapour pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid form. This means when a liquid is placed in a sealed container, its molecules will naturally escape into the air until the number of molecules returning to the liquid equals those escaping. This occurs because molecules in a liquid move with varying speeds and some have enough energy to break the attractions that hold them back and enter the vapor phase.
As temperature increases, more molecules have the energy needed to escape as vapor, increasing the vapour pressure. It's important to understand that a substance's vapour pressure is a measure of its volatility; the higher the vapour pressure, the more volatile the substance. For example:

• Water has a lower vapour pressure compared to substances like ether, which is more volatile.
• Relative lowering of vapour pressure refers to the decrease in vapour pressure when a solute is added to a solvent, as described by Raoult's Law.

Understanding vapour pressure helps in predicting how a liquid will behave in closed systems and in natural environments.

Solution Chemistry

Solution chemistry deals with the process of mixing a solute, which can be a solid, liquid, or gas, into a solvent (commonly a liquid) to form a solution. Solutions are homogeneous mixtures meaning the composition is uniform throughout.
This branch of chemistry considers how different substances dissolve and interact, including common processes such as:

• Solvation: The process of surrounding solute particles with solvent molecules to form a solution.
• Concentration: Measuring the amount of solute within a solution, expressed in terms like molarity or percent composition.
• Saturation: A solution is considered saturated when no more solute can dissolve at a given temperature and pressure.

Solutions exhibit various properties such as conductivity, density, and vapour pressure. These properties can be influenced by the type and concentration of the solute. Raoult's Law, for example, explains how non-volatile solute particles lower the vapour pressure of a solvent. This is a crucial principle applied in solution chemistry.

Colligative Properties

Colligative properties are the properties of a solution that depend on the number of solute particles but not on their identity. This means that such properties are determined by how many particles are present in the solution rather than what those particles are. Some major colligative properties include:

• Vapour pressure lowering
• Boiling point elevation
• Freezing point depression
• Osmotic pressure

For instance, when a solute such as salt is dissolved in water, the vapour pressure of the water decreases, which is described by Raoult's Law. This occurs because the solute particles occupy space at the liquid's surface, preventing some of the solvent molecules from evaporating.
This area of study is vital in understanding how solutes affect the physical properties of solutions, which can be crucial in fields from chemistry to engineering. Understanding colligative properties helps in applications such as preserving foods by freezing or boiling point manipulation and understanding physiological processes in living organisms.