Question

If two liquids \(A\left(P_{A}^{\circ}=100\right.\) torr \()\) and \(B\left(P_{B}^{\circ}=200\right.\) torr \()\) are completely immiscible with each other (each one will behave independently of the other) are present in a closed vessel. The total vapour pressure of the system will be: (a) less than 100 torr (b) greater than 200 torr (c) between 100 to 200 torr (d) 300 torr

Short answer

The total vapour pressure of the system is 300 torr.

Step-by-step solution

Understand the concept of vapour pressure in immiscible liquids

When two immiscible liquids are placed in a closed container, each liquid's vapor pressure is unaffected by the presence of the other. The total vapor pressure of the system is simply the sum of the vapor pressures of the individual components because they do not interact with each other.

Identify the vapour pressures of the individual liquids

Liquid A has a vapor pressure of 100 torr, and liquid B has a vapor pressure of 200 torr. Since they are immiscible and behave independently, their individual vapor pressures are unaffected by each other.

Calculate the total vapour pressure of the system

The total vapor pressure of the system is the sum of the vapor pressures of liquids A and B. Since these liquids are immiscible and exert their vapour pressures independently, we add the pressure contributions from both. Hence, the total vapor pressure is 100 torr + 200 torr = 300 torr.

Key concepts

Immiscible Liquids

When we say that liquids are immiscible, we mean they don't mix with each other in any proportion. They form separate layers when combined. A classic example of immiscible liquids is oil and water. In a closed system, each immiscible liquid maintains its identity and properties, such as vapor pressure. The important takeaway here is that immiscible liquids do not alter each other's behaviors in terms of vaporization.

How is this relevant to solving chemistry problems? Well, knowing that immiscible liquids don't influence each other's vapor pressures means that when calculating the total vapor pressure of a system, one can simply add the vapor pressures of each liquid. There's no need for correction factors or complex calculations to account for interactions between the liquids because, simply put, there are none. This characteristic is crucial when solving textbook exercises or tackling problems in competitive exams like the physical chemistry JEE section.

Vapor Pressure

Vapor pressure is a term that describes the pressure exerted by a vapor in equilibrium with its liquid or solid form. It's a measure of a substance's tendency to evaporate and is temperature-dependent. In a closed container, the vapor pressure of a liquid can be understood as how much the molecules of that liquid are 'pushing' against the container's walls.

Higher vapor pressure means a liquid will evaporate more readily at a given temperature. The vapor pressure of a liquid changes with temperature; it usually increases as the temperature rises. For students tackling vapor pressure chemistry problems, understanding this concept is fundamental. The behavior of vapor pressure is often tested in exams like the JEE for physical chemistry, where students need to apply their knowledge to predict the behavior of substances under various conditions.

Physical Chemistry JEE

Physical chemistry is a branch that deals with the physical properties and transformations of chemical substances. When preparing for competitive exams like the JEE (Joint Entrance Examination), which is pivotal for securing admissions into engineering colleges in India, students must have a firm grasp over various concepts of physical chemistry, including vapor pressure and the behavior of immiscible liquids.

Problems related to vapor pressure require an understanding of the principles of physical chemistry, including phase equilibria and thermodynamic principles. With a high emphasis on conceptual clarity and application of knowledge, physical chemistry questions in the JEE often test a student's problem-solving skills and their ability to relate different concepts. Exercises are designed to evaluate how well students can apply concepts to new situations, making it essential for JEE aspirants to practice regularly and thoroughly understand each topic.