Problem 28 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is false? (a) work is a state function (b) temperature is a state function (c) change of state is completely denned when initial and final states are specified. (d) work appears at the boundary of the solution.

Step-by-Step Solution

Answer

The false statement is (a) work is a state function.

Step 1: Understanding State Functions

State functions are properties that depend only on the current state of the system, not on how the system got to that state. Examples include temperature, pressure, and volume.

Step 2: Analyzing Each Option

Let's analyze each option: - (a) Work is not a state function because it depends on the path taken during the process (it depends on how the state was achieved, not just the initial and final states). - (b) Temperature is a state function because it depends only on the current state of the system. - (c) A change of state is defined by knowing the initial and final states. - (d) Work is related to energy transfer at the boundary of a system, often associated with mechanical work.

Step 3: Identifying the False Statement

Based on our analysis in Step 2, option (a), stating that 'work is a state function,' is false because work depends on the path taken, making it not a state function.

Key Concepts

State Functions

In thermodynamics, state functions are an essential concept that helps us understand various properties of a system.
State functions refer to properties that only depend on the system's current state and not on the path it took to get there.
They give us valuable information about the system at any given moment without needing a history of the process.

• Common examples of state functions include temperature, pressure, and volume.
• These quantities only rely on the present conditions.
• If you know the initial and final states of a system, you can determine changes in state functions without knowing what happened in between.

Understanding state functions is crucial for solving many problems in thermodynamics, as they provide shortcuts for calculations and a deeper insight into the nature of energy and matter.

Work and Energy Transfer

Work and energy transfer are key concepts in thermodynamics that describe how energy moves in and out of a system.
Unlike state functions, work is a path-dependent function.
This means that the amount of work done depends on the specific process taken between two states, not just the starting and ending points.

• Work can be done when there is a movement or change induced by a force, such as lifting an object or compressing a gas.
• Energy transfer is a broader term, encompassing different ways energy can move, including both work and heat.
• Work often appears as energy exchange at the boundary of a system, usually resulting in mechanical changes.

When solving thermodynamic problems, it is important to identify how work and energy transfer contribute to changes within a system.

Path Function

The concept of path functions in thermodynamics is an interesting contrast to state functions.
Path functions depend on the specific path taken between initial and final states.
This means that even if the state of the system is the same at the start and end, the path taken affects the amount of path function change.

• Work and heat are classic examples of path functions.
• The integral of a path function over the process path gives the total change, which differs based on the path details.
• This behavior makes path functions a bit more complex but crucial in analyzing real-world processes where the journey between states influences the system.

By understanding path functions, students can better comprehend why certain calculations depend on the way changes occur, not just on start and end values.